I recently, once again, have been considering looking into a turbo upgrade (from a turbonetics t4 62-1). The car is both street and track driven. It is a F20B/H22A custom setup. Street usage currently at 1bar makes 450whp and the car/turbo has not yet seen high boost + race fuel (2bar).
My goals were in the 600-700 range, but I might now be leaning for more (which most likely will require something larger like a GT42R, etc).

I have been told in the past to upgrade to a GT40 or GT4088R or something along those lines...but can't really see the reasoning, power wise. The maps seem very close between the 2 turbos. Would the large amount of work in redoing a manifold, etc be worth the effort? Would there be a huge difference going from a 62-1 to a GT40 or GT40R?

Please someone lend advice, especially in terms of the similarity b/w the 2 maps:

 

anyone?

 

GT40 56-trim wheel is actually the GT35R wheel

GT4088R should be good for about 700 WHP, maybe a little bit more?