Lucas knows that turbo well. He's one of the first people I ever saw run an old school FPred. I've seen him run great times and blow up lots of third gears with one. /ubbthreads/images/graemlins/rofl.gif
Mitsu exhaust housing or not, I would expect a little more power on racegas. You're not putting down that much more than me and I'm running an old tired 140k mile stock shortblock and a smaller turbo. And just methanol injection, which is nowhere close to Q16.
The FPred uses the large TD06H exhaust wheel and the 8cm housing, no? Tons of people have put down North of 500whp on that turbo, and even smaller FPgreens, which use the same exhaust side with a smaller 50trim compressor wheel. It's not the quickest spooling and transient response is garbage, but it still gets the job done as far as putting down horsies. Something is fishy somewhere within the setup...