Small Emissions leak 99 silverado

Hello, 1999 Z71 5.3L Extcab Shtbox 111,000miles. The check engine light is one but it seems to run fine. Autozone ran the code came up small emisions leak - recomendation was a new gas cap. So i did it and not a thing has changed. Any other thoughts? Also Today it was snowing for the first time I have owned it and the cold seemed to make it hesitate when first starting up.

Thanks

My truck also has the check engine light on. The last time it did that was about a year ago i replaced the cap and i also cleaned the evap hoses and connections on tank and evap canister, cleared codes and didnt come back for a year

The PCM tests the EVAP system for leaks under certain parameters (first off the fuel level must be between 25-75%)...it looks for a loss of vacum over a period of time.
A small leak can be caused by such things as a cracked EVAP line, leaking tank seal, faulty gas cap...to properly diagnos and repair the problem you will need a scan tool and an EVAP system tester which injects a non-toxic smoke under pressure into the EVAP system to locate the leak.