1. That's a common occourance with the GS-R exhaust manifold. It's a double-laywered construction to heat up the cat quicker, but with age it falls apart and makes this horrible noise. No way to fix but to replace.

2. leaking head gasket? Could also be water gathering in the cat or muffler, and being blow out as steam at that exhaust velocity. Though, mind you, GS-Rs don't like to be revved about 3K at a stop unless you're preparing for a drag launch.

3. Compression and leakdown check, plus look around the oil pan gasket, oil pump gasket, valve cover gasket, cam and distributor seals. That should help you identify what's leaking, and whether you're leaking or burning

4. Does it wipe clean like soot, or does is smear like oil paint? If it wipes clean like dust, that's normal (But maybe a little rich). If it's got a bit more of a texture to it, it may be oil residue.

5. Couldn't comprehend, or at least to a point where I could give a concise answer.

GS-R engines can be funny with their oil consumption. After replacing my valve cover gasket, oil pump gasket, tightening down the oil pan, and replacing the cam and dist plugs, my car consumes literally no oil (I'm using 5w-30 w/ 136K miles). Maybe like 1/4-1/2 quart over 3K miles, with regular crosses into VTEC. There has been no detectable change in my oil levels in the past 3 weeks actually, and that's with some very spirited driving and a 300 mile haul on the freeway.

I hear of other GS-Rs with perfectly good compressions using 1 quart every 1K miles, too. But, 2Q every 1K miles is a little too much, and it sounds like you may be burning it. IMO do a compression and leakdown test