I don't see why you want more performance from the turbo. The main item limiting the performance of the vehicle is fuel. I don't know the specifics of the 606, but, I'm sure the turbo has additional capability beyond the current wastegate setting.

If you really want to push more power from it, you need to do the whole deal:
Larger turbo, reworked IP, and an intercooler. Very costly and time consuming to do. But, it certainly will spin the tires.