okk here the story, I just bought a 94 z28 with 130,000 I had my brother check the fluids before we hit the road for the way home and i didnt think he was dumb enough to open the radiator cap after it was hot but he did.... so after filling it back up we drove on the highway for 30mins at 65 mph well ok 80mph just feeling her out never drove a z28 with the big motor.anyway everything was good needs a tune up i think but when i got off the exit i got hung up in traffic an the temp gauge just started climbing and i pulled over and at this point it started over flowing out the resivior so i filled it up again came home put a thermostat in right away used the bleeder vaulve it seems to be ok "maybe" seemed to have good flow.The other problem is the throtle seems to sick open if i tap the gas its like the peddle has a mind of it own and goes alittle further by itself. ??? i know it can be a good car but im pissed. so maybe some help from people who know the motor and the car.thanks for your time bryan

 

Well I think you answered your first question.
You have to so called burp the coolant system when you lose a bit of coolant you get air pockets and it can run hot doing just what you described.
As for your throttle cable Not sure on that one I would make sure everything is lubricated.

 

check out shbox.com for the bleeding proceedure im pretty shure its on there. also your throttle blade prbably needs to be cleaned which causes it to stick. just go get some carb cleaner and spray it on the throttle blade and scrubb it with a rag. be shure to get the throttle bore and both sides of the blades.