Never seen the steel wool and I've had a couple stock exhausts cut to pieces... interesting.
As for the frequency of the muffler Valge, it probably isn't a freq. cancellation based muffler in which case frequency is irrelevant.
Besides, pseudo-turbo == PURE HOTNESS!!!
The stock resonator is a baffled design which is quite disruptive to the exhaust flow by nature. However, yes, with all the other restrictions in the system, you'll never notice any difference other than more noise and resonance. It may remove *some" restriction, but it won't amount to anything you'll ever feel or see in a dyno.