re-rattling

[Shamrock]

Sorry guys for the bump. I just haven't found an answer and I thought maybe to ask the question differently. After I gutted the stillen sports cats and tuned with up-rev, I started to hear a "rattling" noise at 3000 to 3500 rpm (it only occurs at these revs and in every gear.) This doesn't happen when I rev in neutral;only while driving. I tried to video it but it just isn't loud enough. It's a separate noise then the "rasp" that people claim comes from the cats after gutting; however, maybe it is a sound caused by resonance due to the gutting of the cats. Either way it's got my panties in a wad. I couldn't reach a conclusion as to what it is but maybe you guys can tell me what it isn't. I've read so many horror stories about things like crank noise or "knock." Could it be timing? Knock? Crank? Thanks