I went and bought the TFI for my 08 RK and got a great Military discount. Now if I change the air filter what do I need, I have replaced the old paper filter with a K&N filter that sits in the stock housing. Will that be good enough?
If you read the many posts on this, you'll see that replacing the stock filter with the K&N in the stock housing only improves flow marginally whereas the stage 1 intake kit will increase it even more for better flow and performance.