Without going into too much thread hijacking detail, the fuel head has a stack of shims or washers in the fuel inlet bung that can be added to or removed from resulting in a change in system fuel pressure. This only needs to be done if your system pressure is off-spec (usually low) or you pass the 400HP level. You need to have your system pressure in-spec in order for the WUR to operate optimally and before you make any changes to the WUR. When you pass the 400HP level you should increase your system pressure above factory spec and adjust the WUR in concert. These 2 components work together to give you the precise pressures and flow necessary to support more power while starting and running smoothly. Once the CIS is dialed in you can address cam timing, gearing and other components that will increase fuel mileage.
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8