The issue I have with this is that the standard Z4m airbox/filter housing has just the one air input that i can work out from the intake pipe that goes to behind the grille.
The CSL has the snorkel input routed to the bumper I assume, and also an input underneath the airbox, but not sure where this is routed too. In addition you also have the open mouth of the top section of the snorkel piece which on the CSL has the flaps in - so all in all a larger cross section of air input openings, 2 of which might be ram air.
The increased BHP of the CSL no doubt is down to the greater air input, so I am loathed to invest in a CSL intake, and then restrict it by just using the standard Z4M piping - the Goke box appears to me that it wouldn't give any extra air as its a sealed route to the existing input piping, therefore same air volume as a standard intake.
I am thinking that the air input underneath the CSL box, I connect if possible to the standard Z4M air pipe, and then somehow route airflow to the mouth of the box from another location, maybe lower grille area?
Be interested to get opinions?