ICS, CES, or TRM are all great for turbo S52's. Personally, if I were to turbo my car I'd get in tourch with ICS. George seems to know S52's very well and how to make insane power out of them. S54 turbo go speak with Mr.Radowski
He's working on a stock DME tuned turbo setup that should take a dump on anything else out there. The recent drama with HPF and proEFI is pretty scary!
Originally Posted by T.Dot_E30
If money was no object, ship your car to TRM, they've built many e36 turbo setups: http://www.racersmarket.net/
If you wanted to spend even more money and be a little unique: Swap an s54 into it, and then convince the guys at HPF to fit a turbo to it, their e46 m3 turbo kits start at $13.5k + install. http://www.horsepowerfreaks.com/