Air Dog Vs. Fass fuel system mods.
 

I was wondering if anyone has had any experience with the Air Dog or Fass fuel systems. Which one you think is better of if either one actually provides more MPG or HP performance.

Have you checked each website ? They both look like filters,separators and pumps. Dont really think they have anything to do with mpg or hp.
Do you have a diesel or gas engine ?

Neither one is made for the Powerstroke trucks. Not sure if you were talking IDI or powerstroke

Why do you think you need to upgrade the fuel system with such a system as either of those. Is this a pull truck or something of extensive power upgrades. There are plenty of more affordable upgrades or even replacement parts.