I think the highest WHP one I saw was several years ago (talking Evo 8/9 with Mivec) . He made 600+ AWHP and it was a Optima challenge car. Response was better than a T25/T28 combo. So yeah. I am a believer (and have one on my VET and it drives like a V8 after 3000 RPM. Response everywhere all the way up to 8500RPM!)
The current Garrett crop still have a turbine wheel that is a fair amount heavier than the EFR wheels. So yeah.
GLWS! I would still run it as you would literally have 300+ WHP to play with if you ever feel the need to turn the wick up
