Yes, Sean (xman) made 750(ish)RWHP on his Garrett GT42.
Keep in mind, he was on a completely stock 7M (even stock cams, IIRC).
To be honest, I wasn't aware MasterPower made a "GT42".
I know they have a "GT45" model...but that's a whole nother ball game.
(With no relation to a Garrett...