I use BMC on all my cars from Gallardo to 997 and have had no complaints... its a must as the car breaths so much better with it.... And on my M5 the exhaust sound actually got a little more deeper after install....
wait a minute... BMC doesnt have any "drop in" direct oem replacement filters... only the round ones like K&N that suck in all the hot air from the engine... check out this link to BMC's filter... http://www.bmcairfilter.com/VisDetail.asp?ID=710
I just want to replace my square oem filter with a BMC filter... anyone know where I can get one???
Sorry Dude, the S5 has a cone filter inside the airbox as standard but it's card and singe cone. The BMC filter replaces this directly sitting inside the airbox, but is a double-cone (inside and out) and is gauze and fibre.
...Trust me, I have one fitted and have the original sitting in my garage!