after removing the K&N 57i from "Elsie" and fitting the TF 160 Air Filter indusction system I have noticed that the exhaust note is different so I can only assume that the missing part was the induction roar. The K&N 57i is now fitted to the 7th Anniversary Edition as the TF 160 filter bracket won't fit with the resonator box in place and as I have difficulty release the catches on the Standard F filter box it could not remain. The wider TF filter box has catches that I can release. The K&N 57i does have a slight "Growl" to it on the 75th and I am assuming it's noticable due to her still having her original quite exhaust still."Elise" on the other hand has an after market Bosal M/S rear box which has a sporty note but it's not loud ???