hey, when i start my car, i hear a tinny vibration sound coming from somewhere around the passenger rear tire. cant pin point it exactly, but sounds like its coming from one of my cats. or my cat back. any ideas what this might be?

background :
i recently had to take off my cat converter when i fixed an exhaust leak, the pressed bolt broke off the cat converter to downpipe, and i went and bought a regular bolt and nut and tightened it down. changed the downpipe to converter gasket also. i never noticed the sound before, but that may have been because my exhaust leak was so loud.

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1994 Ford Ranger XLT Regular Cab
TMA 360.2 bridged to sub
1 JL Audio w1v2 custom ported box
Kenwood Excelon 5x7 kfc-x682c 360 watt max (front)
pioneer 6x9 ts-905 200 watt max (back)
pioneer deh-p7800mp

http://www.cardomain.com/ride/3087188

It could be a heat shield that is loose.

Heat shield is a good place to start, typically that's the case, but on some occasions the Cat has broken internally and will cause a weird rattle vibration noise. Tap around with a rubber mallet to check the heat shields hell the whole exhaust for that matter, but if you cannot find it, then pound on cat and listen. . .

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Current Mods
White gauges and Temp Cntrl, OHCw/Buggman LED mod,
Bosch +4, Accel Coil Pack, MSD6AL, Walbro, HiFlo Fuel filter,
Custom Ram Air, K&N, Ported / Matched intake, JBA 9mm wires,
Tweeked FPR, EBC 6k's, DynoMax-S CatBack, Jet-Chip, Reflex shocks,
New Anvil Mounts, Timbren's, Optima Yellow, DB 220A Alt. w/4g. jumper,
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