Yesterday I changed the IAC valve to get rid of the fog horn noise and when removing the old one I lost a hold of one of the bolts and didn't see where it went. At worst I figured it went into the hole into the intake. I fished around inside the intake through the throttle body with a magnet on a wire and through the hole for the IAC and no luck. When I fished under the intake manifold and around the back of the engine I found two 7mm wrenches, three intake 8mm bolts, and one 7mm bolt. I though I got the pesky bolt and was pretty sure that one of the ones I found was the one I dropped and after starting the car it ran fine even for a pretty tough 45 min. test drive. Today I can here a tapping when I gas it hard but idling and driving slow and even reving high slowly you never hear the noise, but when you give it a jolt of gas sometimes it does it and other times it sounds fine no noise at all. Do you think this could be caused by the bolt being inside the intake? If it made it all the way into the head would the damage be more severe? Would it go all the way though the head and ruin the short block too? What kind of damage am I looking at if I am truly am clumsy idiot? PS I stopped driving it today and plan on taking off the intake manifold and checking out the intake ports on the heads. Are the intake manifold gaskets reuseable? Also, could clogged cats or EGR problems cause this tap? Also, the car backfired twice today when I reved it and it was tapping today, this engine normally has never backfired, could this all be related? Sorry about the lenth of the post, any help is greatly appreciated.