You can take it to AutoZone or O'relly and they can check the code. I found that out after paying $80.00 for a $2.00 PVC valve at the dealer.
You will get a check engine light on for the PVC valve sticking.
Never heard of the fuel gage problem I had a problem with the temp gage doing that and it was the head gaskets leaking (known problem but not admitted by GM).