areg,
In an effort to understand your modification, I re-read your posted message and came to the conclusion that the "modification" was in driver behavior.
This modification can result in big fuel economy improvements in almost any vehicle (not quite so dramatic without the lean burn feature, though).
There's an ubiquitous disregard for posted speed limits in the USA.
In an effort to advertise the benefits of rational driving behavior, I have a window sticker in the left rear window that reads:
55 MPG AT 80 MPH
80 MPG AT 55 MPH
Unfortunately, it seems as though no one passing slows down enough to read it.