1994 Ford Tempo Car runs, don't run, runs, runs, don't run.

My car will start and run fine except for a high idle, first thing in the mornings. It will make the 30 mile trip to work great until I get into the town I work then at slowing speeds it will die, it will restart and make it to work but may die a few times along the way. After work the car starts and gets out of town fine at slow speeds. Once your on the highway it does good until you slow down for traffic or going uphill, then it dies and will not restart correctly. It will start but barely run, then die. Sometimes after a couple hours you can go back to it and it will start up and make it the rest of the trip but sometimes not. I have checked the fuel filter it was clean, plenty of pressure on the line when I disconnected the filter, I assume that means the pump is good, and I can hear it opporate when I turn the key. I replaced the throttle positioning sensor. NO JOY! Please help.