Hi sorry for revisiting this but my 2000 GTP is doing exactly the same as described in the original thread. Surges/bucks soon as it shifts into 4th, most noticable when slightly accelerating up hill. I am a GM mechanic and i cannot figure this one out on my own. I have replaced the plugs with proper AC delco platinums, replaced both the mass air and throttle position sensors, replaced the air and fuel filters and i always run premium fuel. I have driven the car with the GM scan tool on 4 separate occasions and cannot see obvious data that will direct me to the problem. Did the car in this thread get corrected? Any help would be greatly appreciated.
