mine made 108 rwhp on the dyno, un-modded, 350K+ on the clock. these cars are 20 years old next month.
140kw shown in the book is at the flywheel, manual & brand new.
is yours manual or auto?
do you have the piggy back ECU that controls the cam, should be in the passenger side wheel well, where your ECU is.
a good condition GTS2 stock should pull 125-130ish rwhp on a dyno. my guess after 20 years
mine was a stock standard Auto GTS2 which turned out to not have the piggy back ECU so i wasn't getting the full adv of the gts2 cam.