I saw the thread on the TeamZx2 forum. The guy who did the research (Mechtech) really seems to know his stuff. I asked about my Ranger and after some research and question asking on other sites I am currently trying this one out also. I have only run about 3/4 of a tank through but so far it looks "promising". I'll know more with a few more tanks. My "system" is simple. Put in 10 gallons and try and hit 300 miles or better. Not very scientific and I'm sure someone on here will be sure and point that out, but it's been better than "ball parking it" for for almost 3 years. I did some faster than normal interstate driving this weekend and that may have thrown off the numbers, but for now I'm keeping the resistor in.
Here's a link to the thread. It's VERY long (70 pages), but you'll have to wade through it and pick out the important information.
40+ Mpg