I am going to add some text from the aquatune website which is AquaTune.com - AquaTune Water Injection Systems guys i just want to know what you think. You can go to their website and find out all the info. I have a 2005 F150 and really thinking about adding this feature.

I found this under the testimonials
Hello Nick and the AquaTune staff,
I am totally jazzed! I bought your AquaTunePlus for my ’04 F-150 4.6L engine. Number 1, I was amazed at how easy it was to install. I took a trip of some distance and the first thing I noticed was that it seemed to take forever to come off the FULL mark. The next thing was that my foot was much higher on the gas pedal and the horsepower’s terrific. Now for the best part, I got a 50% increase in my fuel economy! Not bad, huh?
Now I’m telling anybody that will listen what a fantastic product this is.
My highest regards, A. C. from Minnesota