You will see the words PERFORMANCE SHIFT inside your DIC on most newer GPs. You have to turn on the settings in the PCM and get a shift lever that has the PS button on it or you can rig up a switch somewhere else on your console to make it work.
The benefits are nice in the fact that you can have your daily driver tranny setup in nonperformance mode and then have your track or jackin around settings setup for when you select the Performance Shift mode.
Its something well worth looking into. I made a write up for it on our how to section.
http://www.grandprixforums.net/perf_shift.php