I have a 91 accord, everything stock as far as the engine besides CAI. Today, I was messing w/the IAC valve I beleive(right off of TB) and when I shut it off, right after it stopped, there was a cough like sound coming from the bottom of the engine, exhaust area. Its kinda scaring me cuz i hope its not on its last leg.

Its got about 200k on it but runs strong. I think it is starting to burn oil, but its not leaving black on the bumper, or the ground. When I recently changed spark plugs, all of them looked very clean and looked like the "too hot" plugs on the last page of a Haynes manual. Which means lean fuel, and vaccum leaks. Im guessing I should go through, and redo all of the vaccum lines, and see what happens?

But any ideas of the coughing sound, it only does it once.
THanks