Ok, so i have 4.10's and never really driven the rig that fast before but now that i have gauges i put her to the wood for a bit to see what happens. I have no GSK yet and was wondering what happened at 70-75mph. Seems like it defuels/falls on it's face at this speed. I tried to see if it was boost or egt related but it definetly seems like at about 75mph it won't go any faster and even seems hurt and i back out of the throttle. Is this the governor? will the truck run any faster then this? Does the Gsk fix the mph restriction or just the rpm the engine defuels at? P.S. - with the gauges rodding around i can only get 900 -egt temps and 35psi....boost = normal? trans temp never gets above 160... of course its 20 degrees here and the trailer is parked so no towing.... any ideas? I wanna to the AFC mods & smoke screw adjustments soon, don't think the tranny will handle it though.