One more detail, the increase in vacuum with higher rpm is in no load situation. Essentially car is in park. I read around and this is normal as in no load scenario even with bigger throttle opening, the high flow of air due to high rpm and no load, vacuum looks like it is increasing with rpm. It seems as I put the car in gear there is load on the engine which causes the vacuum to go down. Due to the drop in vacuum engine cannot suck enough gas thru the idle circuit, it gets too lean and eventually dies. What is the mechanism in a carb that adjusts this within the same circuit. I presume I am still in idle circuit between 1k rpm and 780rpm right?