I used the EJK on my first trooper ( 08 ) and didn't seem to notice any difference in power. though it definitely did burn significantly more fuel. I toyed with the settings and never really seemed to get any noticeable gains so dialed it back to factory and left it there. I would have taken it out but I removed the cat converter so decided to leave it in because of the O2 sensors. I am now onto my second trooper and am running it stock, no controller. seems to run just as good as the last unit but I can now run all day on about a 1/2 tank of fuel.
In my opinion, the EJK is not worth the money and extra fuel consumption on a stock machine. all that being said, some people have seen gains because of their setups like intake, exhaust, turbo's etc...
I ride mostly in the eastern slopes of the rocky's in Alberta, Canada. so elevations between 4000 - 8000 feet above sea level. not sure if this has something to do with it or not.