Hello
Here is something to think about when considering purchasing a k&n filter.
With reference to the guarantee, I recently returned a filter to K&N. It had deteriorated and I wanted to request a replacement on the so called million mile warrenty.
Their response:
Need proof of purchase, having the logo and product code on is not enough!

If it's older than 10 years your out of luck.

If you have all of the above they can still claim it hasn't been serviced with K&N products, even when you know it has!

This has just happened to me, worst customer service ever, I won't be buying any of their products in the future.

 

I don't know what is the case on the injected models but the older carbed ones are known to run better with OEM filter anyway.

But yea the "unbelievable warranties" are normally just that... who the h*** stores receipts for ten years, specially since these new heat print ones go white in one, two if stored correctly.

 

K&N air filters have always been overrated. Most people don't service them properly (or ever) and end up letting way too much dirt go by.

 

I do. I have every receipt I've ever spent on the F4i since I bought it with 0 miles. I have all the receipts from my original truck [going on 17yrs owning it now] and my 98 gmc since I bought it in 06. Very large binders at this point. If your going to keep something and want to use the warranty, you need receipts. This shouldn't be news to anyone.
K&N's clean flow the same as paper filters. The difference is when they get dirty. Paper elements will reduce flow by a large percentage, K&N's may stop filtering the air very well but they will keep flowing. That can be a big deal in some types of racing.