exactly what im thinking with how heavy our trucks are, the poor old v6 is working overtime.

No, not Nissan.

Iridium plugs?
 

I put iridium plugs and get around 21mpg on flat highway with automatic v6 2wd with 161,000 miles. I would also check for dragging brakes. My front left is dragging now, i think the hose finally collapsed cause i replaced the front right hose and that side quit dragging. Can also get the 3step intake cleaning at firestone or just seafoam your truck.

I think I might try the fuel system cleaner, although I use Shell gasoline and it has additive packages so it is constantly being cleaned. I had the heads off a year ago and the plugs looks fine. Clean burning. I thought a chip would work, but nothing I have read leads me to believe it will really work, especially for the cost.