In the Aug '01 issue of Total BMW (Brittish) there is an article about German tuning co.- Lotech having modified 20 E30 M3's with Garrett T4 turbochargers. 350 hp w/ 14.5 psi boost. It should also be mentioned that the guy who bought the thing blew the engine after 6000 mi. i.e. more hp is inversely proportional to engine life, but I'll bet it was fun while it lasted.