I have upgraded the air filter in the Focus 1.0 Ecoboost to the K&N E2993. Next step would be the 57S-400 kit but at £160 is a bit pricey. However, the filter used in the kit has a detachable disc and this filter is available separately and would presumably fit in the original box. I wondered if removing the disc would have a noticeable effect on performance and intake noise. If you have one, please comment. Thanks.