turbo help newbie

[fottik]

ok i am fixing my friends 1990 240sx he has a turbo in it ball bearing i don't know the a/r the first problem was it wouldn't idle right so i found a vacuum leak, next problem he said was there was a wall at 4000rpm so i was taking the car home and i find this wall. Then the car dies out and because there was problems in the head before with bolts being stripped the camshaft bolt backs out and the timing chain falls off and gets chewed up and the valves get bent. Get that all sorted out and the wall comes back even worse at 3500rpm. This is what i mean by wall when i hit 3500rpm now it will not go past it until i shift the gear and put it in second i have no boost in first gear but in third i can finally see some boost, he has a safc tuner in there i don't know how to use it but i am wondering if anyone else has had this problem, and how to overcome it i know i have to start tuning it but i think it is more than that.