I am still having a problem with a rough idle on my 292.The motor is stock and last year I added the "B" manifold and later distributor as well as a 390 CFM Holley(newer 8007 model).Plugs are good and wires are new.Plugs not showing any abnormal colors.The motor runs great at any speed-except idle.Carb is propely adjusted for mixture and turning screws in cuts off fuel as it should when working correctly.I have readjusted timing backing down a bit from maximum vacuum using the gauge instead of a timing light.I have done a check for vacuum leak and found nothing.If I use a compression gauge what am I looking for as far as possible burnt valves?This motor was rebuilt many years ago and its possible hardened seats were NOT installed at the time and I am thinking maybe valves are starting to go.Any other suggestions?The rough idle has only started a couple of months ago-was not there when I changed manifold etc.