I bought an off brand cold air intake a couple of years ago and I want to change the filter out because it needs it. However, I want to get a bigger filter and I the one I want is a 4'' KN filter but I think my pipe might be a 3" (i'm not too sure about that.) Is it possible I can fit that on there?

 

Get a filter which matches your piping, or get new piping.

 

they sell cuplers at pepboys that will adapt to a larger filter but i wouldn't recommend cotton K&N filters that require oil i would get an AEM dryflow filter or K&N hybrid synthetic filter which is the same filter just red.