Originally Posted by S65NAPWR
Both sound good in their own way. Neither have an annoying drone. Question is whether you want a more aggressive sound or not.
I have the perforated method done to all 4 pipes. It's very nice, no drone and noticeably louder. Like most people said, stock sound when you want and louder when you get on the gas. Sometimes, I wish it was louder when I am driving with my windows up. Than again, If I had done the ACM method, I know I would wish it was less loud when I am pulling into my work parking garage or when I am out to dinner for work.
So, If you daily drive your M3 than perforated mod will make you wish it was louder sometimes and ACM mod will make you wish it was quieter sometimes.
If you don't daily drive your car, than go for the ACM mod.
If there are guys out there with ACM mod who DD their car and not wish that it was quieter sometimes, please convince me to switch to ACM mod