Starting point. Shut off all electrical accessories, close door, deck lid , AC Lights etc. Using the interface cable, connect to the OBDII port. Open the editor program , then turn the key to on (not start) position. Read the entire program and save it. Go your desk and open the PCM file with your editor again. Next delete the anti-theft function and (uncheck) all DTC codes that have to do with the automatic transmission and those that relate to devices such as EGR that you will not be using. Re-flash with changes (no need to write entire). If no trouble codes show, this should put you at the starting point for tuning. That's the basic process.
------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "