I had this problem too. I removed the gas pedal assembly, then slid the pedal itself out from the base. I sprayed some lube on the springs through the back of the base but ultimately I determined the problem was that the pedal was rubbing against the base. The squeak was the plastic rubbing against the plastic. I put a dab of grease on the inside of the pedal and then when I put the pedal back on the base I slid it over to the side a tiny bit to give it some clearance.
I hope this helps anyone else that might have this problem.