Another thing you might want to check is the rollpin in your distributor gear. I actually had this happen on a boat engine once. The idle was funny, and the timing would sometimes jump around, and sometimes wouldnt. Turned out that the rollpin had sheared on the distributor gear and was causing problems. Replaced it and it runs great.

-Nick

1995 BMW 318i
1988 Chevy Silverado 4x4
1967 Camaro
1950 Chevy 3100 pickup