the top speed of a stock gts? 135 was as far as I could push mine. that was with a friend in the car, on a windy night, and with a slightly curvy/hilly road(well they felt like hills)
exhaust, new torque allowed 142mph, although I feel I could have easily broken the 145 mark without one of my other friends(190lb) in the car and with more road(almost missed my exit, scary).
so uh, stock. gts probably = 135-140.at.most