Scotty, I have a 2004 Chevy Suburban with a 5.3. I am getting code 4055 (large leak). I started with replacing the gas cap, that didn't solve it, so I moved on to replacing the vapor canister vent valve. That didn't work either as the code still comes on. Where do I look now for a fix? Thanks, Troy

smoke leak test it as in this video rather than guess https://www.youtube.com/watch?v=PnU-SY6egr4&t=21s