I have a K&N 2nd Gen intake on my Rex. The other day it make a wierd sound. I looked at it and my filter is getting black from motor oil. I took off the filter and i actually poured oil out onto the ground. Why is this?? I switched back to my regular intake and it's fine. What is going on?

 

How long has the regular filter been back on? Could take a while to show up. I had that issue also with the OEM filter. It was an leak in a oil cooler line.
https://www.rx8club.com/series-i-trouble-shooting-95/leak-oil-cooler-line-58015/