Help with wierd launch!!!

[1fast97gsx]

So everytime I launch my car it takes off fine until around 6k rpm and then the car starts sputtering / jerking really hard. I'm not sure what this could be, but it was doing this last year as well. I have since then replaced the engine, trans, turbo, intercooler, injectors, plugs, wires, coilpacks, ignition module and so on. What's left really besides the ECU causing this problem? I only have a problem like this during a hard launch and only in 1st gear. I'm totally stumped herem but I want to take this car to the track!!!

 

[Eclipst]

sounds like a fuel cut problem or a wastegate vacuum line error. Make sure ur vacuum for the wastegate is going into the side of it, not the top. I'm guessing ur using an external wastegate from ur sig.