a mate got a new turbo fitted reciently and i was there when it was being fitted it was done right.heres the problem.when we left the garage for a blast the engine developed a miss or what appeares to be a rev limit at 4000 rpm reguardles of boost setting (16 psi to 20psi) it will even do it with the car stopped and you bring the revs up to 4000 approx.the she limits sounds like bep bep bep bep.........
if you push flat out it still wont go above this rpm even when stopped.
and its not happening all the time but it appears to be getting worse
we have changed, dizzy,crank sensor,map sensor (3 bar),plugs,leads,coil,
but its not making sence as it drove in perfect.its like hitting the sound barrier at 4000 rpm but from idle up to it and beyond it all is ok.i know the obvious thing to suspect is the turbo but it happens also when unloaded and only at one rev setting. i need the guru.s on this one