new 1992 6.5 liter turbo diesle, MPG. VS MPG with modification.

Hi.
First post.
I have a 1992. With 92,000 miles, 6.5 turbo diesle. CK 3500 4X4.
manual transmission with granny, and OD. All stock.
I might tow, 5000 pounds, mostly a daily commuter.

Looking to set up for max fuel economy. If it is possible to gain any thing with air intakes, pipes, .larger tires.

Is this year engine, able to run completely mechanicaly., No Computer.?

There isn't an ECM in your 1992 Truck because you have a manual transmission.

Things that get better mpg are exhaust, proper tires and gear ratio.