Add Bart@AutoCouture in North NJ to the list
They do custom mods installs (Likes suspensions, exhausts, etc.. you name it) and their prices are reasonable. They treat your car like their own and they are very cool to deal with. Bart has an M3 himself so you know what I mean. I had my KW3 suspension installed by them and I am happy with the job. They ordered the part that was missing on my suspension and overnighted it and installed it the next day.
Ask for Sal or Bart
42 Lake St
Hillsdale, NJ 07642