Hey guys, hope you can help me here. My buddy has this cavalier that runs great at any point in the throttle curve besides 3/4 to full throttle. Then it begins to miss fire. We have been having this problem for awhile now. We changed all the coils, plugs and wires, cleaned the EGR, changed the injectors, and changed the fuel pump. And to mention we went through all the sensors to make sure they weren't shot. As of now we are stumped and don't know where to go with this. Please give me some input guys! Its also a racecar so full throttle is crucial!

Just pondering this and you did check the tps for the gradual voltage from idle to full open by hand with a multimeter?Clearly just the key on not running.You have done a bit on the general items I would have done too.Now on the 3.1 does the egr just have the electrical plug going to it.If it has a vac line just remove it and see if that makes any difference.The egr is sealed unit and IF the rubber diaphragm inside it loosing any vacumm it might cause some issues.Next is how old is the IAC as these over time can just wear out and not peform worth a hoot either.I may send a pm to a member here is more savy with the 2nds and let him ponder this and he knows more on these than I.

Did you check injector pulse? Is it actually a WOT issue or is it RPM based? Have you tried going to WOT from idle?