Nothing mechanical has gone wrong with this truck. Things like the seats are worn on the driver side, and the pulleys make noise.
It runs strong gets good mileage for a old truck about 11mpg. I installed a 3" flow master exhaust, K&N Filter, and a Vortec Cyclone. Will melt the tires if you want it to. Very happy with this truck.
Just curious, but what would your idea of "bad" gas mileage be?
Owning a Truck for just 3k Miles, then saying it has never left you stranded does not bear much Fruit.
351w EFI are damn strong motors. They will take anything you throw at them. I had a 302HO pos blow the intake when I was racing an 07 Mustang!