I own a 2004 Impala ss with 93000 mi on it. All stock. Recently I have been experiencing either a misfire or fuel cuts. The car jerks as the engine spits and spiders. This only occurs above around half throttle and above around 3 psi. Idle and low rpm the car runs great no hesitation or misfire whatsoever. I recently changed spark plugs to the ac delco iridium. While performing this task I broke a Vacuum line that goes from the throttle body to some kind of regulator for the fuel system. Fixed the vacuum line and all is good. About 3 weeks later is when I stated experiencing this problem. I would not think that this has anything to do with the plugs or the problem would have started right away. Plus if it was a spark issue you would think that it would misfire throughout the entire rpm range. There is no check engine light. I got mad the other day and held it floored and let it jerk and spit and the check engine light came on and flashed for about 30 sec. Then went back off. This one is getting the best of me. PleAse Help.