1994 Ford Mustang • V8 2WD Manual • 148,000 miles

I have a 94 Mustang gt 5.0 with 148,000 miles. I just put new manifolds, off road h pipe and flowmasters on there. At first it was all fine and dandy. Then a couple days later I noticed my rpms going from about 500 to 1000 back and forth at idle. So I took my IAC valve off and cleaned it. It helped for a couple days. Then it started to shake at 1000 rpms when it was either cold or rainy, but it was fine in good weather. Then it started doing it all the time when I start it and at idle, but fine while driving. It then started to make a clunking noise at idle and as it is turning off, it sounds like something was turning, then just falls and scraping. There are metal shavings under and to the right of the water pump and above to the right of the crankshaft pulley and harmonic balancer. Does anybody know what these shavings are from and why the engine is shaking so bad?
May 16, 2011.

Possibly a bad idler or tensioner pulley bearing?

Aug 13, 2011.