I'd noticed my exhaust pipe (b/w the cat and muffler, just before it curves right) was hanging pretty low, probably 4-5 inches. I mounted it back up and attached three stainless hose clamps around the heatshield and under the pipe to keep it in place. But now I've noticed that when I step on the gas there'* quite a bit more noise (though nowhere nearly as much if there were no cat or muffler). Any suggestions on an insulating material to absorb the vibration to pad the hose clamps with? Or maybe an alternative way of clamping up the exhaust pipe in this area? I couldn't really find anything nearby that looked like a place where a clamp had gone before. Thanks

There are universal hangers that have an exhaust clamp on one end, a metal strap with holes on the other, and a rubber-like material connecting the two. The metal strap with holes can be bent as desired, and the holes are for screws/bolts to attachment points on the chassis. As you learned, you can't have metal to metal contact between your exhaust and the car body or the vibrations make their way into the passenger compartment.

Also the factory exhaust system has vibration dampening rods welded on every major bend after the cat....

Over time the welds brake and they come off resulting in extra vibration or resonation as what your describing.

Take another look under your car and look for little metal blocks about 1".....one one each bend of the exhaust after the cat where the rods were welded at one time. Are they still there?