High RPM's

This happens only in the summer, I live in Florida, so summer is like Satan's bathtub. If it is cool outside because of rain or at night, then it doesn't do it in summer either.

The truck will start fine and run fine until the heat of the day 90° plus, then it wants to run away on its own. It will run at extremely high rpm and makes for hard shifting between gears. I can make it slow down if I brake enough (without pressing clutch) in a gear to make it try to stall, then down shift and repeat process to first gear at which it will go to a normal rpm until I press the accelerator to resume driving, then it jumps right back to high rpm's. I took it to Autozone to read the code, they told me it was the canister purge valve solenoid, so I replaced it, no luck. I also replaced the TPS. That did not work either. I replaced the TPS because I could unplug it and the truck would run at really low rpm's and never act up, so I thought it must be bad, I was wrong.