Ran the truck for a while with the vac gauge hooked up a little bit ago.
Pretty steady reading in the 14-16 in range without much bounce or wiggle....when it's running smoothly at fast idle with partial choke. If I back off the idle speed or try to push the choke all the way in....vac gets bouncier, lower, and the engine eventually dies. Sometimes with a backfire.
From looking at this
chart ...I guess my next move is advancing the timing?
