NO MODIFICATION NEEDED, this plugs right into the valve cover and uses two o-rings that are provided for perfect tight fitment

 Flapper Delete Fitting for N54

WILL NOT WORK WITH RALLYROAD FUEL RAIL THAT HAS A RETURN FUEL SYSTEM

 AS SHOWN IN PIC (NOT THE PURPLE FITTINGS)

also known as the flapper delete fitting for the n54 powered vehicles , works better than competitors variant which only use one Oring.