AKRS1

I have a s2 which is starting to annoy me. I had it tuned on the rolling road last month at PE and it made 203bhp but the piper cam i had in the engine was knocking so i decided to have it replaced and a new piper cam kit was fitted. Had it on the rolling road and its misfiring or hesitating at around 5200rpm. The new cam was checked over and its fine also i have had new injectors fitted and although the car feels better to drive, the hesitating is still there. The cars been for a full service so i dont see it being the spark plugs or anything like that. The guy at PE reckons its a fueling problem does anybody know whats going on