Mate the guys at Herrod have designed this piping to replace factory without the use of xr8 air box as obviously it is not needed or they would have altered there design.... Don't mean to be blunt but if your doing everything else to your car maybe there induction advice or just change filter if it's for street! I have run there setup and tune all day long on track and couldn't fault it... Give the guys a buzz or come check mine out.