After driving approximately 15000 kms on a "standard" 540iX I upgraded to the official BMW MPPSK kit.
This gives me solid experience to compare before and after.
Here is how the exhaust looks from behind:
As you can see, the exhaust ends are larger and not sloping as the original ones.
Apologies for the blurry pic of a dirty car
At least it's fast
Well, to get it out of the way - the MPPSK makes a great car a
fabulous one!
But it also imbues the 540 with a slightly different, more naughty and raucous character than its original, wafting and silent, refined persona.
Let's get the one negative out of the way - there is a slight drone from the exhaust, regardless of setting, on highway speeds. A drone that wasn't present before. The 5 is a silent car, after certain speeds (say 120km/h on terrible Swedish asphalt) the road noise overtakes the drone, but if you're sensitive that is something to consider. I am sensitive and am not bothered.
Other than that it is all great! The car sounds definitely louder and sportier - almost Audi S6 like. There is more noise, sharper shifts, even some crackles and pops (though nowhere near as pronounced as the M3s or the 340i MPPSK). So I think BMW nailed the perfect compromise of a grown-up 540 with slightly more sporty characteristics.
Now, on WOT people turn around and look! Previously there was no such reaction.
Other than the sound, the MPPSK is supposed to raise hp by 6% or 20hps (from 340 to 360) and torque by 11% (from 450nm to 500nm). I think it is fair to say that this is extremely underrated. I haven't dynoed the car, but the difference feels waay more pronounced than what the numbers suggest.
My butt dyno says way closer to 400hp!
The car pulls notably harder, there is new enthusiasm to rev to the red line, the shifts are crisper and tighter (there is a new torque converter installed), overall the car is transformed! My wife loves it!
Overall, I think that the MPPSK is tremendous value and warmly recommend it. My only gripe is that there should've been an option to get it like that from the factory.
Here is a clip from inside the car, with a window lowered inside the garage - this is how it sounds from the inside on startup. It is nowhere near as loud as my M3CP, but way nicer and more characterful than original
https://youtu.be/g2WK66VYVJw