backfire = bad O2 sensors? long

[dinomite]

I see that you have the fuel pressure as low as it goes, but it may not be low enough, could still be runing rich. You said you've cleaned the plugs, do you know how to read plugs? cause that would tell you if you are still running rich. That would be my guess. Also, with the stock H-pipe and the cats still intact, but no air pump, the cats will eventually clog, I doubt that has anything to do with this, but it could cause problems later. Your injectors might be to big, I'm assuming your running a 190LPH fuel pump with them, no? To fix it you need to even out your fuel flow with the performance of the motor, get a supercharger! But seriously, you may need smaller injectors/smaller (150lph) fuel pump. Anyone else? seems kind of odd to me.