Ok guys,

I have an 05 Tahoe that has about 6k on it since rebuild. About two weeks ago I got a stumble while driving in town and the dreaded flashing check engine light. When hooked up to a scan tool initially I had a MAP sensor code, so I replaced it. Needles to say that didn’t fix the issue. I am having misfires on all cylinders. Ran a smoke machine, and no visible vacuum leaks. Cats are both good, and no backpreasure measured. Fuel pressure was good.

What the hell can be causing this? At normal driving RPM’s engine runs horrible, but seems to clear up at higher RPMs. Doesn’t matter if it’s cold or hot, runs horrible. Tahoe was dyno tunes months ago and was running flawless. Has some detonation sounding pinging when giving gas at lower RPM too. I’m at a loss.