I don't think anyone mentioned the details of this one yet, but the SMALL K&N filter we tested was about 2.5" of filter media in a cylinder, it fit really well but it was *HILARIOUS* hearing this filter on the dyno. The intake sounded like when you stick a vacuum nozzle on your skin, pffffffffwwwwwtttttt!!!!! The car was obviously not getting the air it needed and it would knock randomly, making it perform super inconsistently.
Also, we made it a point to not test the stock airbox. It's been widely proven that aftermarket intakes make power over stock, even with tuning. Let's not kid ourselves here. Besides, that would then require us to change the intake pipe, put on the air box, blah blah blah. Too many variables to change! Besides, I took off all of the brackets for my stock box almost 3 years ago. I have them, but hell if I'm putting them back on the car!
Incidently, my old-style buschur filter is officially for sale; pm me reasonable offers
