2000 Toyota Solara Start Just Fine Rev Wont Miss Out Die Actually Take Off Down

i have a 2000 toyota solara and i can start it up just fine and i can rev it up and it wont miss out or die but when i actually take off down the road it wants to die. it will loose all power and the radio will shut off and the rpm gauge will hit zero and it will come right back out of it sometimes and a few seconds later it will do it again. i had the alternator tested and it was fine.