I'm currently using the K&N. The miniscule power that I think I feel is probably all in my head. Gas mileage hasn't went up or down so all I can say is that I think I feel a difference but the 5 hp you might get from it you really shouldn't be able to feel. The way I look at it though is that I won't have to clean it for 6 months or ever have to replace it.
I haven't used one with my Z, but I have with alot of my other cars. I've always noticed a difference, some cars more than others. In my Saturn I didn't notice much of a diff, from when I went from a K&N drop in to a Short Ram intake. If that helps at all.
A forum community dedicated to Nissan 350Z / 370Z and Infiniti G35 / G37 owners and enthusiasts. Come join the discussion about performance, modifications, troubleshooting, exhaust, turbos, maintenance, and more!