As rossco said, the only way to get more power from your current turbo is to upgrade the exhaust housing and screw in more boost, which could be risky if you don't know what internals have been upgraded.

The best bet would be to get a larger turbo and stick with current boost levels (and give it full boost (19.5psi) to redline if you want), if the turbo is more efficient the same boost will give you much better power levels. See Ballistc's graphs when he changed from a VF22 to a TD06.