Not sure if the setup would be the same, but I know a lot of V8 Chevy Trailblazers/Silverados/GMC Sierra, Etc.have issues with the Purge/Vent Solenoids and just the "EVAP" system in general. If you have a check engine light on I'd recommend getting the code pulled to see what it is, and post it here. IIRC the codes are between P0440-P0459, but in my experience it is usually P0441, P0442 and P0443 that I see in GM vehicles.
I had an '07 Silverado with a 5.3 and ran into this issue, fixed the solenoids and canister vent valve, and it made the odors go away. Another issue I commonly ran into was the fuel pump nozzle would shut off if I was filling up with it all the way in and on "auto" I would have to hold it at the very edge until one day it would only let me do 10 cents at a time. Talk about a breaking point....
I'm sure Cordell or someone who has a much better knowledge of GM products in general will step in here and give a few better ideas.