I have a 2002 envoy. So after I cleaned my throttle body, and wow did it ever need it, my gas gauge is acting funny. When i first start it up, it reads what its supose to. Then once i put it into drive and drive even a foot, the fuel gauge reads almost empty and my range goes to 30km. Then when i put the envoy into park and sit for a couple seconds its goes back to where it was and so does the range on the dash. Then i can put it into drive and its fine, until i shut it down and start it again and it does the same thing. Ive done some searching on this and some say it could be the fuel sending unit is either going or is just gumed up with deposits. Do you think that could be it, or something else?