TME makes the chips and www.tme.com should have power curves.
I think they also have notes about exhaust requirements and
recommendations.

The best way to make more power is more boost. Freeing up the
exhaust is a good step but there are no major gains without more
boost (and that may require a larger turbo at some point).

The wastegate setting does not affect max power -- it changes the
way power comes on in that it allows the turbo to idle at a faster
RPM (so there is less turbo lag). Take it too far and you change
the linearity of the throttle converting it to a on/off switch.