Originally Posted by john_S6

The biggest difference came from removing the flap inside airbox. I had BMC air filters prior but I made the mistake of cleaning them with air hose and they got damaged. Between both BMC and K&N I do not notice any difference. However if you remove the flap inside airbox the amount of air flow will increase the car seem to have faster pickup. Also once the temperature reaches about 40F then it turn into a beast, not sure why.

Originally Posted by TwoSnails

Did you remove this flap with the stock filters? I wonder if this would make a difference. Where is this restrictor flap? Or is this something you can only do with aftermarket intakes? thanks

Originally Posted by john_S6

The flap is part of stock airbox, once you open airbox to replace the air filter you will see the flap at bottom facing the engine. Not sure about stock filter performance, I removed the flap after BMC air filter installation.

Originally Posted by TwoSnails

where did you get the bmc's? Do you still have them?

Originally Posted by john_S6

I have K&N installed in my S6 and it was easy job.

Originally Posted by Leeladisky

How did the K&N filters fit???? Were they OEM level fitment? Any gaps?