OK, my exhaust is this:

DC 4-2-1 1 piece header
RandomTech High Flow Cat w/ new gasket put in when I replaced it 30K miles ago
GReddy Evo exhaust

Somewhere during VTEC engagement on a hard acceleration and with the car moving, I get a loud pop and a raspy rattling noise coming from the exhaust note. If I have the car still, with the engine in neutral, and blip the gas past VTEC and the same point the noise normally occours, I don't get the same noise. Before I thought either the cat had broken or a resonator was failing, but that wouldn't make sense because I would think that noise would occour both at a stand-still rev and while accelerating. I'm starting to think that maybe the cat gasket flexes too much under acceleration or a heatshield is going bad (I already removed all the heat shields directly connected to the cat, so I'm thinking it's the heatshield that sits between the cat and the shifter. Anyone know:

1) The torque specs for the spring-over bolts holding the cat to the header, and
2) If I were to strip the heatshield immediately between the shifter and the cat, would I experience any negative side effects?