Toyota Repair: Low idle, blown head gasket, coolant loss

Question
Ted-
I asked a question yesterday regarding the low idle rpms of my 1990 toyota 4runner V6, which adjusting the idle didn't seem to help.  I decided to try to narrow down what the problem could be.  To answer your question, it idles smoothly all the time, when the idle is low I can't even hear or feel the engine running.  Also, I have noticed no smoke, no coolant loss, no abnormal oil usage, no coolant in the oil, and no power loss. Also during the tune-up they changed my spark plugs and said my wires were fine.  Is there still a chance it could be a tight valve, blown head gasket (which was replaced just over 50,000 miles ago), low compression, or a misfire at idle, or does this sound like an intake leak?  Is there a way to test the intake system for leaks?  (my intake is a K&N fipk, not the stock one)

Answer
If it idles smooth then we can rule out  a major engine problem, there is no misfire, has anyone set the engine timing, an intake leak will also cause a rough and erratic idle, one last suggestion that may help, remove the throttle body and clean it including the vacuum passages, this might solve the problem, it's worth a try.