I've seen t28 go past 310whp pretty easily here with little effort. Shoot, a buddy of mine is making 303 on a t25 hybrid and ran a 12.5 with a 2.3 60ft. His setup is stock maf+safc, 550, t25 hybrid, full 3 inch exhaust, fmic 14psi spike drops to 12 by redline.
Depends on what he other mods the op has also.