straight L-elbow works just fine for me after mine broke. replace with new hose clamps if necessary

Not sure how many miles are on your 370z, but would the factory emission warranty respond to correcting the problem? I think that warranty may extend to upwards of 100k miles but I'm not certain.

18k miles and I am guessing this is a 3yr/36k mile warranty item......so with a 4 year old car (even with low miles) I am pretty much screwed.

I would suggest that you check since I'm fairly certain that the emissions warranty lasts much longer than the drive train warranty. I don't have the warranty booklet handy right now. I seem to recall that it may be 4 years or 60,000 miles. May be worth a phone call to the dealer.

reason why it's completely clean inside is because it's the fresh air ducting for the CCV system - otherwise there would be a huge vacuum inside the crankcase. the filthy side is actually via the 3/8" hoses at the front of the intake manifold/collector

I've heard that piece acts like a "muffler" and actually dampens the sound of your intakes. I wana remove mine and make me st8 tube.

it does act like a baffle of sorts. how effective it is, i'm not sure.

but i'll give you my 2c. the Stillen G3 CCV barb on the right hand side pipe (bank 1) is narrower than the diameter of the stock accordion pipe's CCV pipe.
because of this, i had an idle which kept sagging when stationary. i cut off the Stillen barb and welded on a larger diameter barb and the idle was rock solid afterwards. No ecu resets or relearns were performed either.

so, if you plan on deleting the CCV barb on the stillen pipes, my suggestion is to not do it. after all, the ccv system on our cars works by drawing away the crankcase fumes and drawing in fresh air at the same time. that volume of ingested fumes is accounted for in the combustion calculations by way of the MAF sensor because the fresh air that gets drawn into the crankcase to displace oily fumes comes via the Stillen pipes. I hope this hasnt confused you too much :) what i'm trying to say is that you dont want any unmetered air in the system (eg. by fitting a small pod filter and blocking the barb on the stillen