not trying to hate but, honestly just do some research. There are millions of these threads that already have ALL the answers to your questions that you might possibly have. And instead of waiting for people to reply to your post you can just look them up yourself.
And just to save you time here is the low down. if you have the money for the PE get it. its honestly amazing. I get compliments non stop on it. it will cost ya around 1200-1300. it you want something a little cheaper that is almost is good get the AA exhaust. Its very similar to the PE but is like 800 i believe and you can get them used believe it or not for like 500-600.
2008 E90 N51 328i
- Depo Blackline taillights - 6000k Angel Eyes - Headlight Daytime Light Coded - Performance Exhaust - Performance Intake - AA Stage 2 -Red Cyba Scoops
- Front Windows 15% and Back Windows 3% - Two 10inch JL Audio Subs