I just recently purchased AA x-pipe and HFC and unfortunately I have to sell it
(as is) ... I had it on my car for about 5 days and it was enough to piss off my neighbors ... I have Eisenmann Race and with AA pipes / HFC it sounds awesome ... but whenever I start my car it sets the alarm off on my neighbor's car and he is definitely not happy with it
About AA pipes:
1. The quality is very good
2. Perfect fitment (both e90/e92 M3)
3. You can definitely feel increase in power/torque right away
4. Amazing sound
I believe Active Autowerke sells them for around $3300.