I've had them on my bike for 8 months. My opinion is that if you aren't having ignition problems they won't make a difference. My dyno's back me up, at least on my bike. I always do before and after dyno runs whenever I make a change, whether it's exhaust, cams, coils, and even different fuel calibration maps. The before and after dyno for the coils, on my bike anyway, was undetectable. But, I wasn't having problems before I changed them out either. That being said, they are worth the money for looks alone! I'm glad I got 'em !