Hi, I purchased a 1994 3.4 Camaro about 3 weeks ago. When i bought it the check engine light was on and the it sounded like the cat was clogged. The check engine light will only come on when you leave it in gear and let it back rev at a higher rpm. Today I had the cat changed out, new fuel filter, plugs, wires, cap and rotor done. But now for some reason when I push the gas pedal down about 1/2 way and i am in 3rd or 4th gear at low rpms it sputters and almost sounds like a back fire. I think it may be my egr valve or an o2 sensor. any input would be most appriciated this is my first gm.

 

Do you know what code is causing the light? Both EGR and O2 sensors being bad can cause sputtering. Though I'm leaning more towards your EGR valve being stuck open.