Now that I have it installed I find that until I used the bias on the MAF sensor the computer was throwing in extra fuel. Now that that is done I am realizing 12 to 18 % gain in MPG.
2 interesting things on the ford are. A my exhaust is spitting water, lots of water, the others installed did not do this to this extent, secondly, the exhaust is clean, I mean to say the exhaust does not throw black like it did before install.
For something that does not work, it has some interesting effects on my wallet.... So best miles per so far is almost 26. (55 mph on a day that was about 76 degrees, the hotter the worse it is) My RV (non cat) went from 11 to 16, that was a smaller system. Going to retrofit it after these results.
You can build one for under $30 if you know what to do and get. | 
