That's my goal (450 realistically/safely) with nearly the same mods. 2.5" exhaust, and MSP mani's look to be the only difference power-wise.
Last year I was @ 350 with stock IC piping and my own street tune. This year I've got V3 massive intercoolers and 2.5" piping and CNC'ed OEM throttle bodies. Unfortunately I won't be able to chime in for a little while yet as I still have to finish buttoning everything up.