[Rob B]

Originally Posted by marxjunk

what about the timing chain? So much slop it bounces around or the teeth on the nylon gear...if theres no vac leak, youve got gas and spark..what else could it be? pontiacs are famous for eating timing chains...

i think you found the answer yourself there....

I never ruled out the chain and gears and thats probably the issue. It's just hard to believe a motor from that era would last 166000 miles on an original nylon geared sprocket and stock chain. From what your saying and maybe I'm just interperetting it wrong, it sounds like once you get to a certain RPM, it will idle/rev and sound fine but only gets wierd when you go below a certain RPM.
I'm trying to help you do a few simple things to check a couple of the key things needed for an engine to run. A compression check is simple and can eliminate so many variables and at the same bring those same ones back into play if you get so funky readings.