I have a 1999 camry. The check engine light keep coming on. I have replaced the EGR valve and cleaned the EGR valve plus the mounting pipe leading to the EGR valve and the throttle body.I used throttle cleaner. I have done this a number of times and the light comes back on. Could it possibly have anything to do with over filling your car with gasoline?

Yes, you can do a lot of damage to the EVAP Control System by overfilling the gas tank. What exact code is being thrown?

Check the EGR vacuum control solenoid (follow the vacuum line back from the EGR) It is located on the back side of the engine These have A high failure rate Hope this helps.

Biff26 hit the nail. P0401 EGR insufficient flow detected. Very common on your car. Not easy to get at, but not too pricey either.
Should replace the egr modulator also.