If you havent already, go through and change out all the basic wear items....spark plugs, cap, rotor, wires, air filter, fuel filter, t-stat, coolant, oil.
You can install a manual boost controller and raise the boost a couple pounds. I believe stock is 7, and you can raise it up to 14 without hitting overboost with no other mods. Opening up the exhaust will help the turbo spool faster.
A t2 conversion should be in order before you go looking at a different calibration, check out
http://thedodgegarage.com/turbo.html for info on that, and info on just about everything. After the t2 conversion, you will need a different calibration, look for one for a shelby Z (or upgraded one for a shelby z, which will require a 3bar map and larger injectors). A big intercooler should be installed around this time too.