I have completed the homemade tymar upgrade and the truck seems to run the same sound is little better. What performance benefit do I get from this? I did it mostly for the security of knowing no dust would get in my motor.

What is the next upgrade I should do to get better milage?

 

If you have not added fuel flow, i.e. a chip, then the performance benifit of the intake is nil. It will keep your exhaust gas temps down. A larger exhaust would also help in this matter, but until you add fuel performance will not change much.

The single most effective upgrade for better milage is putting your right foot on a diet.