2004 Silverado 2500HD Problems

I have a 2004 2500HD with a 6.0 gas that for a couple of weeks kept giving me a tighten gas cap warning. This would happen every moring going to work and it would happen within a few feet of the same place every morning. After several days of this one morning the check engine light came on. The gas cap warning has not come on since. That same day I got gas and the truck started then shut off and was really hard to start. This now happens every time I get gas then after that it starts fine. I had the code read and it said PO496. Can anyone help with this?

Remove the evap line from the purge solenoid and unplug the electrical connector. with the engine running there should be no vacuum at fitting on the solenoid. If there is the solenoid is either bad or there is something holding it open

Remove the evap line from the purge solenoid and unplug the electrical connector. with the engine running there should be no vacuum at fitting on the solenoid. If there is the solenoid is either bad or there is something holding it open
Hay Airjer thanks a lot for sharing your answer