I have a new rebuild in my 95 k2500 350 Tbi. Running really rich. Acts like only running on 6 or 7 cylinders checked all the plug wires for resistance, the 0-2 sensor is good do you think it could be a vacuum leak through the throttle body? Any suggestions would help

 

O2 sensor won't have anything to do with it. Running rich, I don't understand? I'd recommend checking the plug wires for proper placement.

 

I already checked the plug wires. I had my distributer 1 tooth off when I set the valves/rocker arms. I think my valve timing is off. I'll redo them and see if that fixes it.

 

I meant valve lash not valve timing. But I redid the valve lash with no results. I also checked compression and have cylinders on both sides reading 0 - 10 lbs and the rest reading 120 - 125.. The chances of two bad head gaskets seems like a stretch but anything is possible. And it could be valve timing but before I pull the timing cover I'm going to run some more vacuum tests. Vacuum reading can say alot if you know what to look for but I was so convinced it was valve lash I didn't pay enough attention to them. Tomorrow is another day we'll see what it brings.