I was wrong once again. Fundamentally wrong. But where exactly hides my mistake – a bit later. Let’s keep the intrigue.
In the beginning, a short explanation of how “standard” exhaust and Performance kit versions for F30/32/36 work and where the differences are.

Standard exhaust

Peculiarities of the standard exhaust:
a. in the exhaust pipe (1), two little resonators.flame suppressors are integrated;
b. the exhaust muffler (2) is created in such a way that the noise (flow) of the exhaust gases is suppressed in the labyrinth and is released in the atmosphere via the top (in the image) opening, but in the opening of the right side (15), the exhaust gases are getting with minimal resistance – only several barriers;
c. in idle, in the stage of warming up the CO catalytic converter (first 60 seconds after starting the engine); in driving conditions of small and average load, the valve (13) is closed, and the exhaust gas in the atmosphere is released only via right side (look from the behind of the car)/top (in the image) opening;
d. in the driving conditions of a large load (high RPM and ample required torque at one time), the valve (13) opens, and the exhaust gases are released in the atmosphere also via opening (15). Taking into account that the opening (15) has much lower resistance of the gas flow, in the extensive load modes exactly, it (15) becomes more “active” in releasing the exhaust gases;
e. the valve (13) is managed electrically, and management is handled by DME. Management signal: 0/12V. Supply of 12V closes the valve.
Why such “debauchery”?
For several decades, the supervisory authorities of the automotive industry have been struggling to reduce the loudness of exhaust systems. The aim – a more comfortable life for us all, and the passing cars would not interrupt our sleep, etc. At the same time, car enthusiasts are craving the opposite – real “roaring,” which would complement the performance of the IC engine. The car manufacturers, instead, are struggling with reducing the costs and sizes of each component of the car.
This valve (13) solves all problems. While measuring the exhaust noise (both for certification and during TI, it is performed when the car is standstill, without a large load), the valve is closed, and the exhaust noise is minimal. The muffler (2) performs its duty. In the modes of large load, the mufflers (2) task is made more accessible by the valve (13), which opens, and the most significant part of the exhaust gases are released in the atmosphere “directly”. Accordingly – the manufacturer can reduce the size and efficiency of the muffler (2), but the car’s owner gets a more sporty sound of the exhaust on the mode of max load. Everyone is a winner!

Performance and Sound kit exhaust

The exhaust is modified in the following way:
a. the little resonators/flame retardants are gone in the stage till the muffler;
b. the exhaust system is made symmetrical – on both sides of the muffler, the valves are placed (now there are 2 of them), the exhaust gases from Y type divider go to the muffler, from it – in the atmosphere;
c. the valves release exhaust gases into the atmosphere directly, without a muffler.
The image from under the car:

How does the Performance exhaust work?
a. during warm-up of the CO catalytic converters (60 seconds after starting the engine); ECO Pro; Comfort modes and Sport; Sport + modes, if you drive calmly for a while (5+ minutes) – the valves by default are closed, and the noises of the exhaust gases are suppressed in the muffler. The car’s exhaust: quite bassy, but at the same time – without excessive noise, and, of course, fits all noise standards. In previously mentioned modes, the valves are opened only in driving conditions of large load (high RPM and ample required torque at the same time);
b. Sport; Sport+ modes, if you drive dynamically – the valves are open for all time (even in idle), and the exhaust gases are released in the atmosphere, bypassing the muffler. The exhaust of the car – loud. So loud, as if with a removed muffler.

Impressions regarding Performance and Sound kit
For now, I have driven around 1000 km in different modes, and I’m ready to share my first impressions of this product.
a. the dram of all “sporty” drivers of aggressive, loud enough exhaust, which compliments the roar at the moment of release of the accelerator pedal with “popcorn” – fulfilled for 100%! In Sport and Sport+ modes, the exhaust is a “straight pipe’, at the same time – with no problems with TI (just switch to Comfort mode);
b. all this time (more than a year), while I was driving this car, I was annoyed by the “clumsiness” of the engine. The reaction of the engine to the accelerator pedal was… slowed! Yes, the detention was only part of the second, but it was! The engine’s nature did not correspond to the car – “carting”/aggressive, sporty coupe. With this kit, the situation has changed RADICALLY. In Sport and Sport+ modes, the reaction of the engine is momentous. Touch the accelerator pedal – get the hit on the back. Even the Torque indicator arrow nervously shivers when reacting to each unevenness of the road/each slightest touch of the accelerator pedal. This fundamentally changes the temper of the car and senses when driving aggressively;
c. I have no objective measurements, but subjectively – the turbo aggregate is used more aggressively. With all the previously mentioned changes, the subjective contribution of the kit is much more impressive than the mathematical 10% of torque and power. The car has turned into a provoking sports car;
d. After installing the kit, I noticed that the DSC/DTC performance had changed completely. During the first time of acceleration, the car allowed the rear axle to slip and blinked the DTC indicator in KOMBI. DTC adapted quite quickly to the tire grip and did not allow slipping in Sport mode anymore. At the same time, the performance of the DTC has changed significantly. Previously the car “got tired” while switching the gears – when the next gear was switched, the torque dropped (DTC reduced it for the car not “slip away”) and then, during some half-a-second, reduced full torque. Now the DTC works so that the torque does not drop while switching the gears. A nuance that is very important to me. My experience says – even if the readaptation (restoring) of parameters of any module is necessary after upgrading the software, the old adaptations are typically not deleted. The old adaptations are forcibly tested if there are no fundamental differences in the hub performance – “put in place”. This time, the DTC module did not use old adaptation values, which allows me to conclude that the software changes were so significant that they required a “new start” for this hub.
I was wrong when I said that this was my most useless purchase. I was wrong. This is a special purchase. This purchase transformed a boring car into a car that gives pleasure with each acceleration. From each curve, drove.
Finally – let’s compare a typical “chip tuning”, in which (even if we assume that individual upgrades for fuel and/or boost map are created) some DME parameters are cheated (which inevitably “throws” it in the limp mode) and solution, in which:
a. not some separate maps are cheated; not the appeared error messages are deleted, but the margin of the required torque is exchanged; all management and adaptation maps are adapted to new conditions; coefficients of the calculation of the energetical module are changed;
b. other modules are informed regarding the new threshold of torque and power (for example, NBT, which now correctly displays increased torque/power; DSC/DTC module, management of the gearbox, if such exists);
c. reaction of the engine and transitions processes are changed significantly;
d. management of the turbo aggregate is changed;
e. management of the exhaust valves is changed – it allows to enjoy the sound of the “straight pipe” in the automatic mode;
f. algorithms of DSC/DTC module management are changed;
g. the exhaust system with a lower counterpressure in extensive power modes is installed, which ensures a 10% increase of torque in the range of 5000 .. 7000 RPM.
Summing this up, is EUR 4 .. 5.000 (a typical cost) a lot for this upgrade? The price of the new car (with B58 engine) is above EUR 60.000. For a 7 .. 8 % price increase, you will get a 10% increase in power/torque and a completely different car. From this point of view – no, it is an honorable price for a quality product. My rating: is 10/10. All due respect to the BMW engineers.