What would cause a 91 Stanza to buck and not allow you to go over 65 mph unless you shut the car off and re start You can be going 75 and exit and not don shift and when you speed up it bucks?

The issue you're experiencing with your 91 Stanza could be related to a problem with the fuel system, such as a clogged fuel filter or failing fuel pump, which affects the engine's ability to maintain power at higher speeds. It could also be linked to ignition system faults, like worn spark plugs or a malfunctioning ignition coil, causing misfires under load. Additionally, the transmission may be slipping or experiencing issues that only reset when the engine is turned off and restarted. A thorough diagnostic check is recommended to pinpoint the exact cause.