Right where do i start finally finished fitting my new project in to my sierra 4x4, managed to get hold of a couple of kits for a sierra dohc and rebuilt the engine to mate i up to it. Had a pig off a time to fit it as i was short of time due to this being my everyday car. After finding a load of faults got it running and it goes brilliantly EXCEPT that it dont seem right on boost. If you give it full throttle it goes but feels like its holding back, if you then let off the throttle to about 1/2 - 3/4 it takes off.

This car is not your off the shelf turbo as to control the timng and extra injector TT have used an extra ecu, loom with additional map sensor so it makes it a harder to trace faults.

I am a novice to turbo's as i have always had n/a cars so please any help as to what my hesitation could be would be appreciated.