I have literally replaced everything I could think of that is causing this rough idle, honestly I also think the tahoe is idling a little low in gear @500rpms... first to start, it is a 07 tahoe ls 4x4 with the AFM/DOD flex fuel 5.3 engine... I have pulled the heads because of a collapsed lifter on #1 (afm issue), replaced all gaskets topside, new plugs, wires, all 8 coil packs, mass air flow sensor, running 93 octane only in it, and it still has a rough and low idle in gear and at a stop... I don't know where to go from here, please help I've never had one I couldn't beat, but this 1 is really pushing it...