I've had 2 similar noises lately: First one was the number one plug unscrewed itself anough that a tapping noise was coming out the plug hole. Second was after I did the TC, etc and it turned out to be the air pump (A piece of keyway had been lodged in it and when I R&R the pump while doing the TC, it came unlodged).

Good Luck.


84 4RUNNER,22R,HEDMAN,WEBER 32/36,Davis Unified Ignition,33" BFG