Well i got the exhaust yesterday...wow what a package. I think the reason that you pay so much for ACS is because of the packaging. It came in a huge box with all sorts of foam and fabric in it. Quite interesting.
So i took it to have it installed today at the same shop that installed my M5 exhaust. They gave me a rip because they hated the M5 exhausts but i told them this should be much easier.
Well they took off the old one and just about cried because it was so heavy. They made numerous BMW engineering comments, all in good humor.
As for the ACS exahaust...went right up with no problems. Looks good from straight behind but the tips look a little long from the side...nothing a ACS rear diffuser cant help but certainly not bad at all.
As for sound,
idle- slightly if only louder but deeper. Very nice, you can tell it has an aftermarket exhaust but it does not have the aftermarket exhaust tone (did that make sense?) due to the deeper note.
moving- it sounds great when below 4000rpm, deeper and more pronounced but zero resonance. I tried to make it resonate but it didnt want to, a welcomed departure from the B&B's on the m5. Very established sound..very close overall in sound to the stock one but with a deeper set of complex tones.
BUT. Above 4000rpm the exhaust just gets drowned out with the rasp from the rest of the exhaust system. Its not that bad but it certainly needs to be addressed. (I could deal with it, but the girlfriend might not like it). I think this exhaust in conjunction with the rasp-x pipe would be nothing short of amazing. I take a guess that adding any exhaust is going make it worse but im glad that now there is a fix.
Thinking now, the B&B's might have had a slightly better overall sound but generally they loose the aftermarket exhaust sound and sound exactly like stock in the upper range...so for the m3 it would be like 4000rpm and might have led to resonance. I have enough of that with the M5, no need for more. Now im not 100% sure the B&B's would have been like that but, thats their characteristic market sound. At 4000rpm is where the ACS takes shape but with the overtone of rasp. Clean that up and it should be music to the automotive junkie ear with the beauty of the tips. Im sure that the ACS/Remus will have much better overall quality as well.
performance-ahh dont care. It didnt feel like much although im sure it may do 2-3 hp but the reduction in weight makes it seem like more although i cant judge 4 hp...can you? Also the whole aftermarket exhaust mental thing might be there too...not sure but im not looking for performance.
wish i had a digi cam to take some pics and make a vid..but i keep spending money on mods.