i've been using one for about 6 months now. no noticeable change in power, but definite protection. i had a couple times last summer driving in rainy conditions when i suddenly got a CEL and my car went into limp mode...upon inspection of my MAF sensor it had water on it. since i got the hydroshield filter i've never had the problem, and it also keeps the actual cone filter clean. it's much easier to take off the hydroshield filter and clean it every so often than having to clean the cone filter all the time (if you're constantly driving in dusty/sandy areas like me).