engine mods

Does anyone know if the engine in a 91' Q45 can be stroked or highly modified. Seems like a great platform, V8 power from a japanese automaker. The tolerances on the engine seem to be very tight. I am working on an M5 challenger as a bet against a friend who owns an M5 and would like some info on performance parts other than intake or exhaust. If I happen to come across any I will let you all know, but at this point there seems to be very little or none and any help would be appreciatied. :banghead: