I have a bone stock 2001 Ford Excursion with the 7.3 Diesel. I talked to guy who said I could gain 3-5 MPG with a 75 HP chip and a 4" exhaust and down pipe kit and an air intake kit.

Has anyone done any of these upgrades and are any of them worth doing?

It looks like it has a 3.5+" stainless exhaust now, could be aluminized pipe.