05 GTP Comp G Engine Stutter
 

Hey guys wondering if you could help me out here. I recently just purchased an 05 GTP Comp G that the previous owner didnt take care of at all. I had the car in for service not too long ago to get the plugs and upper O2 sensor changed. Now the car stutters to even accelerate at a decent speed, I can get up to 75-90 but no boost from the SC without having the CEL flash when I hit the gas hard. Someone please help me out here.