I agree with Paul, If you just want to upgrade the turbo and leave everything else dont bother. because your gonna be stuffed. I am running a gt-2540 and yes its hard to get the power to the ground because the wheelspin is crazy. If you want to upgrade the turbo, upgrade everything that goes along with it. Fuel pump, injectors, intercooler.
Also PaulR33 the GT-25 series are built with an internal wastegate so an external one is not necessary and would just be a waste of money.