86 Chevy Truck Question..

Hey guys, Happy Thanksgiving to all...

Well, I have an odd ball question here, but here goes..

I have a dullie 86 Chevy TBI 350 utility truck. Bought it about 5 months ago, and it has 150k on it. Automatic, 16 inch wheel 3/4 ton.

Anyway, the only bitch I have is it gets 4MPG.. Now I know it is a heavy truck, but I don't have it loaded with tools. 4MPG!!! This is killing me. My buddy had a 86 Chevy Roll Back and with a car on it going down the highway gets 9 MPG..

I did the basics..Air filter,pcv,fuel filter and plugs...Now it does burn a little oil, but any ideas out there that might help me?? I know it isn't a hot rod, but hell, most hot rods with .600 lift cams do better than this thing..

How are the injectors?