Hey mate.
These are great turbos indeed, but infact are actually only rated to ~560hp and real world results on the dyno thread have shown these to be at thier limits at around the 340awkw (450hp) mark, the response & midrange is great making these the perfect turbo for street use according to some but i think 600hp+ is abit off the mark.
Anyways thats my 2c GLWS mate.