[xlr8or]

An inconsistant idle could be many things. I was having that problem and it turned out to be the distributor. The mechanical advance wasn't returning all the way on an intermittent basis so it would idle high until it sat for a bit then would start dropping as the timing returned to normal. Might want to check the timing on the car before and after going for a run as well as watching the advance with the timing light to see if it resets as the RPM drops. Might want to pull the cap and rotor to check the springs on the advance.