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.

I assume sense 75-90 are not public road speeds you mean at the track as we do not condone illegal activity.

Does you check engine light flash rapidly when it shutters?

You have a bad coil.

That is correct on the track at those speeds . It flashes at the same speed of the seat belt warning light when you start the car then it goes off after a while not long though.

I've heard it could be a bad coil, read on another post that it could be an issue with the fuel pressure regulator, someone else told me it could be valve compression. Just at the end of my rope with this.

I'll put money on it being a bad coil, or bad plug wire. https://www.gmforum.com/trouble-shooting-test-procedures-141/testing-coils-spark-plug-wires-278818/ A cracked spark plug can also do this.

To test your FPR just pull off the vacuum line and sniff it. If you smell gas, the FPR is bad.

I have seen 2 times a bad misfire caused by a broken valve spring. A compression test will not show this.

Just that with me just buying the car less then 5 months ago to have to do all this now is extremely frustrating. How would I be able to test to see if its the coil pack? Plugs were recently replaced and thats when I stopped getting the CEL code for misfire. Now if it were a broken valve spring and a compression test would not show my next course of action would be?????

Click on the link I posted. Tells you how to test your coils and plug wires.

Only way to check valve springs is to remove the valve cover and look. The chances of that being the problem is very small. Most likely problem is a bad coil, or a loose plug wire.