I was a few months ago because someone had mentioned it on a different forum who bought some for a different bike because the power gain that Motomaxx claimed was pretty good for a low cost (those were aluminum not carbon). However the guy ran a before and after test on the dyno and it didn't make squat for difference. In fact it ended up putting less power by a fraction of a hp with the Motomaxx stacks and the dyno chart showed pretty much no improvement anywhere in the rev range. So he was pretty disappointed that he wasted his money.
So I'm not sold on it and ended up not getting it based on that. I'm not saying Motomaxx was straight up lying but you know how it goes with dyno tests. You can tailor the parameters and have some variables in the test to make it look like you're getting more or less power, and nobody knows how they did their test. The guy I talked to did it on the same dyno, by the same technician, with the same parameters, etc. He eliminated as many variables as possible and even customized his fuel map again with the new stacks to optimize it and I think that gained him like 0.5-1 hp only.
2007 ZZR600 (sold)
2006 CBR600 (sold)
2010 1198 (parted out across North America)
2013 CBR500R (race bike)
2009 ZX6R (race bike)