Korman auto has a turbo for your engine. It will put you up around 230hp and 240lbs. For about $5000. It also will retain its bullet proof reliability. good luck. I'm planning on building a more powerful engine for my '89 325is. I'd like to get 250 hp. I could build the hell out of my m20, transplant an m50, or how about an engine from an E34 M5. Would the M5 engine fit? Also, I'm not sure if I like the idea of putting a different engine in my car. What do you guys think?