I've not seen any 2JZ-GE data that supports or refutes this claim, but I've seen
lots of data on various other engines that refutes it. It's on a case-by-case basis that depends on induction and header resonance as well as cam timing. There is no rule of thumb that I'm aware of. If there is 2JZ specific data, can you point us towards it?
My turbo IS has a full 3" exhaust from turbo back. No catalyst. There is a magnaflow resonator, and a HKS hi-power muffler with a big fart-can tip on it. It isn't loud at all. I mean, louder than stock, but not "loud". Mind you, I'm 41 and well past my loud pipes phase of life. Even the woman doesn't think it's "loud".
I bought the car with the system already installed so I don't know where it came from, but the quality and construction looks like a real company made it; not some random exhaust shop - and then somebody spliced the resonator in later.