5.3l idle issues.
Ok I have a vortex 5300 in my 04 Tahoe. All stock. I thought I would ask here first, considering it is an Ls/lq base platform. When it's at idle its running extremely rough. Headlights are dimming and it feels like a misfire. I treated it like a misfire, did plugs, filters, cleaned TB, checked for vacuum leaks, all general maintenance stuff. That didn't fix it. I dug a little deeper, pulled the intake manifold, checked for cracks, pinched/bad gasket, nothing. It isn't throwing any codes, so the computer isn't picking up whatever it is. It should be noted that we just replaced the heads with 706's. The old ones were cracked. It was done by myself and a good friend who is a former GM master tech, and this issue started shortly after. Myself, as well as my friend, cannot seem to find the problem. I don't want to go to a shop and have them shotgun parts at it hoping it will fix it. Any help is greatly appreciated.