Tuning a vortex 135? Clean it, relube it, shoot it to break it in. As far as the piston power, you can really only reduce the power of it. You can't increase the power of the piston much more than it already is set by the manufacturer. Make sure all your screws stay tight- the barrel pivot in particular. You could fiddle with the trigger assembly a bit- honing some components to smooth out the trigger pull if it feels rough.