I've decided to turbo the M by early spring, I'm working on a custom kit with a friend of mine (2000 328Ci) they should be rolling out at the same time. I'll post the details later but I'm looking for 400 to the wheels early on - the engine has 90k miles on it as is, 8.5:1 pistons will probably be needed so it's possible that I could be looking at 450-480 to the wheels.
I've caught the bug, I need boost (and a fast car.) Watch out.