Okay, so my 2004 V6 Mustang has 2003 Mustang GT dual exhaust ran through straight (true dual) pipes...I used to have high flow cats, but they where busted & rattling like crazy. I got rid of the cats and just welded pipe in place as a temporary solution. The rattle was non-existant for probably a month and now it's back!! NO cats! Exhaust rattle! All fasteners/bolts are tight and nothing is rubbing anything! What could it be? The rattle only really occurs from 1700-2100 RPM and is especially HORRIBLE sounding at 2000 RPM (louder rattle) The rattle seems to be worst when I let off the gas, say, to shift, or just to slow down...any ideas?