Couple years ago I looked into all these types of things. Did'nt try this particular one though.
I did do the acetone test on 3 different cars. Two were FI and the other a carbureted car. The two FI cars saw very very little gain. IMO not worth the effort. (2003 V8 mountianeer & a 94 GP) On those two cars I saw the most gain in steady state freeway type of mileage. But for around town driving I saw nothing. Since my driving is 50/50 & I was averaging 0.5mpg better.. I decided it really was not worth the effort.
However!! My 87 MCSS (5.0L w/4barrel) most definenately saw an improvement in smoothness & mileage! I was shocked actually. I even had to adjust my idle speed down! On that car I saw an avg of 2.5 to 3.0 mpg better in 50/50 driving. No joke.. it made a significant difference.
The acetone thing is the only one I've personally seen work. But.. IMO it's not really worth the effort on a FI engine. The way fuel is "injected" into the intake port on a modern FO motor, it's already atomised very well. Adding acetone just gains so little.
btw, I've now started to do this for the ranger. I'm carefully keeping a log and will report when I come to a conclusion.
He who is enslaved to the compass is free to sail the seas