Have a 2001 Pontiac grand am gt with the 3.4. After replacing fuel pump and filter with new parts, I'm getting 42-43 psi of fuel pressure at idle. I've ran a snap on scanner on it as well as drop down tests on the injectors. Everything checked out and no misfires. The 02 sensor upstream jumps around alot, from Mid 100's to mid 800's. Would that be an issue? Running regular gas ( 87 octane), no aftermarket parts, and car only has 130k on it. I'm stumped and could use some help as my other vehicle is a diesel and it's over 5 bucks a gallon currently lol.