1994 toyota camry le v6 3.0 liter dies in drive

Hi, i own a toyota camry le automatic that has the engine light on and dies while driving. I've taken it to a mechanic and he diagnosed the error codes p0500 and 720. we fixed the 720 by replacing the trans. speed shaft sensor and replaced the vehicle speed sensor with one we bought from ebay. The rpm will shoot up randomly whilst the check engine light is on. the speedometer works just fine now. car dies when it slows down or at a stop. the rpm goes far below 1000 and i smell gas then i hear it beginning to struggle just to stay on. the dash lights dim and return to normal then dim again and repeat then it shuts off and the battery light along with oil light come on. turns on fine but when put in reverse or drive it shuts off. it cant go more than 3 minutes without it messing up. when the engine light isn't on it runs just fine but once it turns on i've got about three minutes to get back somewhere safe. also when it does want to die i have to give it gas for it to stay on. i feel a major lag also and the o/d light flashes along with the pwr light. i really appreciate any advice anyone is able to offer.
thank you.

It appears that the P0500 code has not been cleared. Check the wiring and connections and then test the new VSS