I can say now that I have run everything from a 12 to a 21, and I like the 16-18 housings for my all around use. I traded my w-g12 for a nwg16, straight across, and will never go back to a 12.
I had a H1C/14 for a while, but noticed little difference in EGT or boost over a 12 (both high).
I then went back to a 18 (sold housing for extra cash). No difference in EGt, less boost. Tells me the engine worked less to get the same boost, and was overall more efficient.
Bought my stage4 turbo (used from ebay- $350 to my door). Put it on, with the 12 on it and ran it for a while. Similar EGT to the 18, with much more boost. Compressor size (60mm/ 6wheel) offset the extra restriction of the 12.
Traded for the 16 (ported). Put it on. No gain in EGT, lost 4-6psi boost across the board. Peak EGT might have gone up 50deg, but a 30deg difference in ambient temp will do that, too. Once again, the same scenario as when I went from 14 to 18.
I will keep my 16 for now.
With a stock intake hose, PG7 air filter, and 4" tail pipe (ok, 4" from teh transmission crossmember, but still stock ahead of there), I get plenty of turbo whistle, at idle, acceleration, and cruise. So much, that I am looking into more sound insulation if I start towing again. Turbo pitch gets on my nerves at 75-80mph. Part of it is the straight exhaust, part is the compressor upgrade.
I agree with Forrest- the HX35 will whistle well, silencer ring or not. On my 91, I didnt notice any difference with or without it.
Daniel