92SC Ok, I must be getting closer, running out of things to check. Doesn't stall, but just rough enough to be annoying and scare passengers. Replaced head gaskets, wires, plugs, motor mounts, cleaned TB and IAC both of which were not dirty. Idle speed is ok, slight raise doesn't smooth out. Car has about 90K miles on it. Closed off main vacum source, no difference in idling, vacum about 18 on dash when warm, 10 when cold. No error codes, checked by dealer. Does IAC go bad slowly or is it go or no go, it appears clean, but I guess this and MAF should be suspects?? Plugging out IAC shuts down engine, squirting air into MAF changes engine speed as expected. Please help....should I buy an IAC? MAF, or new head of hair....