sounds timing related to me, or lean. where did you get the setup? if your sure the on boost fuelling is correct then l;ets assume timing. do you have a std cam/pulley? a wild cam+std pulley could cause a timing issue. also is the dizzy ok. firstly though try new plugs and/or inspect plug gaps. plugs dont last long in rst's. oil seal in turbo would be diagnosed by a. smell oil b.smoke on overun when upto temp. smoke will be almost white with a blue tinge. the oil leaks into the hot side and when hot becomes more apparent. for what its worth your issue doesnt sound turbo/seal related. just out of intrest what fuel do you use? are you using the amal valve?