Re: Rough Idle & Stumbling
Hmm, did you get a misfire code for the #5 plug? And a lean code now as well. Do you have a scanner with live data? Would be good to check your fuel trim figures. Eventhough i told before that the filter/pressure regulator should not be the problem, these new events could point towards a (too) low fuel pressure. With a too low pressure, the PCM will compensate with a possitive fuel trim, until +25 i believe, and then it will set a lean code. If the mixture becomes too lean, it can start causing misfires.
Also a bad O2 sensor can be your problem. If it sees a lean mixture, while it is not, it will add more fuel and finally show the lean code.
So i would first check the fuel trims and the O2 sensor readings. The O2 sensor(s) 1-1 (and 2-1 if you have 4 sensors) should fluctuate between 0.2 and 0.8V.
If you have a fuel pressure tester, then you can also check the fuel pressure itself, which should be around the 45 psi.