I have recently tuned up my Gen2 turbo for the spring. (plugs, plug wires, cap, rotor) the engine runs great in gears 1-4 under any kind of acceleration and in 5th gear under gradual acceleration. Under hard acceleration in 5th gear at 60+ mph, coming up a long hill, the engine "bucks" and hesitates. Back off from the throttle and all is fine. Any help would be greatly appreciated. Could this be a simple timing issue? ... and how should it be set?