2004 Scion xB dash lights and gas tank filling problem

When attempting to put gas in the tank, the pump just shuts off. I had to slowly (cents at a time) add gas, just barely squeezing the handle on the nozzle. If I added at a normal rate, the pump kicked off, gas overflowed from the fuel tank spout.
Upon starting the car, the CEL, VLC and "track off" light came on. I drove home, disconnected the battery to reset codes and drove for a day or 2 until lights came on again.
Took it to auto parts store for code reading-read a code stating something about purge control valve. The guy wasn't sure so another came out to check it. Lights were off and no code was read.
Car runs slightly differently when lights are on- when cruising up to a stop light, the engines almost wants to stall-it did on one occasion. When the dash lights were off, no problem.