Hey Scotty! I have a 2001 Silverado with a 5.3 Vortec. It's giving me codes P0440 and P0452. I already replaced the gas cap. The truck has no symptoms except a lot of pressure build up in the gas tank. Air comes gushing out sometimes when I take the gas cap off. What could be the problem Scotty?

often a bad evap cannister vent valve