DET is short for the RB25DET, which is what GTSts have. basically, you have a DE, non turbo, hence T stands for turbo
D= Dual Overhead Cams
E= EFI (Electronic Fuel Injection)
T= Turbo
and for the record, i think handling mods, even cheap ones like sway bars and strut braces, are a good investment no matter what power levels you have