1) In stock 180 hp trim, those IHI's strangle the 2.3's they come on over 5000 rpms. 2.3 liters sounds like a lot of displacement, but they have about the same specific output as a stock LS engine with the turbo removed... maybe a bit less, since I spooled my .60/.48 and my .60/.63 a lot quicker than 2.3T do.
2) Tiny turbines and dainty turbine housings are not safe. The engine cannot handle excess heat, and the only way it gets out of your engine before it melts it down is through the exhaust. Which can't flow against the tiny IHI restriction. Heat builds up and can't be shed effectively, detonation sets in quick.
3) Tiny compressors worked at or a bit past their maximum blow really hot air. So now you're shoving more heat into the engine.
I was serious, 230 whp the smallest I'd go (looking for safety and reliability) is OEM T3 turbine, preferrably .63 AR. Not that AR with OEM T3 means that much since they have a very small "stage 1" turbine wheel that can only pass so much exhaust, but sometimes the small things add up.
With stock LS cams, significant boost before 4000 rpms is nice, and makes things easy to drive, but it's not particularly fast until 4-6500 range. On the other side of the coin, significant boost before 4000 rpms also leaves you open to a lot of high combustion "dwell time," for lack of a better word. Instead of the heat staying in the exhaust, it has enough time to bleed a significant amount into the engine itself... thermally loading everything and setting you up for detonation/engine death. Time is one of the unholy triumvirate of detonation. This is why high rpm boosting allows small engines to crank out some power and still be really, really reliable. You won't hit 230whp in the lower to mid rpm range without shitcanning a stock LS, IMO, you have to rev it. *shrug*
One of the D15/D16 boys would love your IHI, if you were slick you wouldn't have to fork out much more cash to upgrade. It *is* the biggest factory IHI (I'm aware of).
Hell, if Jeff Frank is having good luck with those $5/pop SSAC T3/T04E's, that's the route I'd go. Stage 3 turbine wheel/housing, and feel free to go with a smaller AR turbine if you're that worried about spool. It'll fucking rip, you can get some exhaust (heat) flow past the larger "stage 3" turbine wheel, and the sexy bitches will want to fuck you AND blow you, instead of just blow you like if you run the IHI.
