I would venture a guess that the turbo spools well after 4k rpm. As for building a "highway monster" a lot of the Supra guys seem to do it and I can't really wrap my head around it. With that much more thrust one would certainly want to get wider wheels/tires, a firmer suspension and bigger brakes regardless of whether or not the car is going to be on a race track (aside from a drag strip of course). But hey chalk it up to me being a fan of the balanced approach.