I have a 96Z with 3" flow pipes 343 gears my car is pissing me off i changed all the wires and new plugs brand new fuel pump. the car will run great when its cold but when t hits 170 or above it will start hesitating. It will start running doggy ive put a 160 t stat in it need tech help thanks, Larry Smith

 

no SES light?

sounds like once it goes into open loop after warm up something is going bad. could be a sensor, which isn't being used till after it warms up.

 

Thanks man i got octane boost today longshot but did nothing i dont think there is way of finding whats wrong check engine light isnt even on.