is your dizzy gear worn? and have you had a chance to ppull the timing chain cover to inspect the chain??

 

Finally got to the bottom of it tonight. I thought I would re-check for vacuum leaks with propane this time instead of WD-40 and I found a vacumm leak where the intake manifold meets the riser plate for the carb. I tore everything down and I had the wrong gasket on it. Duh! After getting the right gasket ordered, I was disapointed to see that there is about a 1/8" gap that the gasket doesn't cover back where the pcv hose hooks up to the riser plate. So I bolted everything back up, the truck runs 100% better but there is still a small vac leak back there. Hmmmm. I thought about putting a small piece from the old gasket back there or trying to seal is with RVT silicone. Is it a bad idea to use silicone on that riser plate? Let me know, thanks

 

Been having similar issues. Read where some people have taken the heat riser off and use sand paper or file till flat. Can check by setting heat riser on a plane of glass to check for a flat plane on heat riser. Plan on trying this tomorrow, if you do go easy and check riser often till square.