K and n filters will destroy a turbo. Not so much the oil but it will let too much dust into the turbo .vanes. it just is not worth 1 or 2 more horsepower to spend the amount of money on a new turbo. Now this is coming from my guy that had a 6.0 powerstroke. I have not had my ego boost that long. But the concept would be the same. My 2 cents keep it stock.