whaat is goin on?

ill cut to the chase, sometimes when driving at a certain throttle position there will be this type of hollow roar sound... not too sure how to describe it, but it's very distinctive. Dunno what this could be, cat, muffler, exhaust manifolds, ignition, what? it almost sounds liek a lot of air roaring through somewhere... yet also has a sound liek its going thru something metal, a hollowness...

Its the cat trying to get out of the glass.

Is there any noticable change in engine response?
Because it sounds like its either wind noise getting in through a dodgy weather seal, or just tyre noise on a rough tar seal surface.

it's definately not tire noise. the engine bogs down a little bit when this is going on, not too much. if i let up on teh gas or give it more it stops, but if i hold it at the spot where this happens (and it's different every time), it keeps doing it

It could be the rear end making the howling noise. My Fiance's 95 firebird has a similar noise.

Then my guess would be a blown gasket on the inlet manifold, or a leak in the exhaust somewhere that is opening and closing up from flex in the system as the engine is reved and the car travels over bumbs.

Since its a roaring noise I would start with a check of the intire intake system, from filter to manifold.