Been dealing with these problems on my95 Z28 for awhile now. Finally got a extended hose to check pressure under load because car is running like crap again. New injectors, filter and regulator. Car is at 40 psi maybe 42 under 3/4 to WOT, on the street under load. Backfires like crazy through intake. Prepared to do the pump but want to make sure I am not chasing my tail. Opti maybe? Or what... Thanks in advance, been pullin my hair out I need some help!

 

I recall when one of my optis was going out it would backfire through the intake. The rotor screws backed out and the timing was slightly off. Replaced opti and problem was fixed.