[ddsmith]

I can honestly say that I have never seen a car engine that would do this. You must have no overlap to draw that kind of vacuum.

I have about 27 inches of mercury on vaccuum gauge

But back to the question. The idle mixture screw should be adjusted toward the lean stumble direction from the highest vacuum. When you get the lean stumble reverse direction on the screws about an 1/8 th of a turn. Make sure the choke is working correctly. If it doesn't fully open adjust it so it is when warm. What the h*ll is up with emission checking a truck our age? This stuff is all a bunch of crap anyways. The government way to make more cash. Emission checks here cost $14 every time you go and then some moron who doesn't know squat. Drives the vehicle on the tread mill. They usually suck so it takes three times longer than if I was the one driving it on the tread mill. Oh well. What can you do. Other than moving somewhere that doesn't test.