I was driving yesterday and went to pass a car and ran it up thru the top of 3rd gear. After about 6K RPM I noticed an odd chattering. Wasnt a constant chatter but like an on/off chatter. Never heard anything like it before and did some "tests" and ran it up through 3rd a few more times and same thing, after about 6K RPM it happened. So I slowed down and did some more "tests" and ran 1-3 out and 1 and 2 didnt do it at all, just 3rd. Well today I noticed it in 2nd gear when I was accelerating. I slowed back down and eased on the throttle accelerating but not in boost and nothing, but when I'm in boost I hear the chattering now. Its not real loud and like I said its not a constant thing, sorta sounds similar to a chattering flywheel. Im pretty concerned cause I'm not fond of messing anything up and havent the slightest idea what it could be. Anyone have any insight or a similar occurance?