Did anyone else experience the same problem: I have a scoupe turbo with a rebuild engine, ported head, intake etc. with removed catalyst and straight open muffler, but otherwise stock as fueling and ecu is concerned even the air filter is stock.

At first it was runing just fine, then I crashed it and it stood still for about two years. I bought a new car and swaped the engine and then the problems started. Almost every time when I floor it in 5th and sometimes even in 4th gear it starts to accelerate and when it gets in the upper rev range it starts to jerk violently like a missfire or fuel cut usualy twice in one second interval and then I let of the gas and sometimes it sounds like a backfire in the exhaust.

I then mounted a front mount intercooler and changed injectors to 300cc but it's still the same, maybe even worse. It does this only at WOT and when the speed reaches 170-180km/h or more, if I hold the pedal at about half throttle so only 2 orange lights are lit it gets past 200km/h (120mph) no problem and very smoothly. I suspect it's related to being on full boost for a longer period of time, because it goes through first three gears too fast to cause it.

The main question to me is, is it fuel, boost or spark related? The fueling should be very rich becouse of the injectors, but as I said it was the same with stock ones, the main concern here is if the fuel pump is a problem since it's from a non-turbo scoupe (don't know if they are the same). Boost is at it's factory settings so it shouldn't be a fuel cut (I suspect fuel cut takes the fuel completely and the car looses all power not in intervals) unles the boost controler is not working properly (is it possible it stays closed if malfunctioned) or there is a boost leak (does the ECU read MAF when on WOT?). So only thing left is spark blowing out or maybe bad wires. I sure hope it's not detonating, but then the engine would be blown long ago.

Any help is much appreciated, thanks!