So here's my 2 cents on K&N filters. I agree with Jagular. I don't know whether our Jags have Bosch Mass Air Flow Sensors, but my last car did. The K&Ns can contaminate the MAFS relatively easily, and often when they do, the car shows no easily detectable symptoms at first. You do lose power, but you don't realize it, as the power goes away slowly. You can clean the MAFS to restore some of the lost performance, but it seems that once contaminated, the MAFS contaminate more easily, as the restoration only lasts a short time. A lot of my fellow M5 owners were surprised at how much their engines would "wake up" with fresh MAFS after running their K&Ns for a long time. While many people have never dyno'd their cars, you finally figure out the power loss when you have trouble passing other cars you easily could out-pace before, or you finally get to the point you get an engine light.

I know a lot of people swear by K&N's benefits and have not experienced the above. I would say a lot of the problems come from over-oiling the filters, but for me the minimal gains are not worth the risk or worry.

 

Bryce,

Yes, it is the jaguar extended warranty.