Is your charging ok mate? i had something similar before on a friends car when the alternator wasn't charging causing popping and banging.
Or how about your tps, havent you changed your inlet and throttle body doe's your tps not need setting up.
Are you still on autronic management can you not plug it into a laptop and check for fault codes?

Just a few ideas mate i might be way off the mark but worth a try befor you break it ha ha