Pin length in the WRD, is set to make sure that the extra cold idle air is closed off at the correct temperature. This is "ground zero" for the WRD adjustment. The oval shims adjust mixture during warm-up. The barometric compensator has round shims which can adjust the fuel injection at all speed ranges and temperatures. The more difficult "rack adjustment" also adjusts the injection at all speed ranges and temperatures. The large slotted screw on the intake, adjust idle air (all temperatures) but mostly used for warm engine idle. The thumb screw on the back of the injection pump adjust fuel mixture up to about 1,500 rpms (all temps), two dark color screws inside the injection pump (rear governor springs) adjust mid-range (1500-3500 rpms) all temps, and two light colored screws inside the injection pump (rear governor springs) adjust high range(above 3500 rpms) all temps.
Before making injection pump settings check make sure your engine is in good tune. Make sure your engine linkages are correct, your ignition timing is correct, your distributor is working properly (vacuum retard, advance etc), and the fuel pressure and volume is correct. The barometric compensator on the IP, and the "heat feeler" in the WRD can also be defective. When the baro compensator goes bad, the injection usually goes lean. The WRD "heat feeler" can be measured or tested to make sure the cold engine idle air operates and closes off when it should.
Start by checking all tuning items and make sure the cold engine idle air closes off when it should. Next determine and adjust the fuel mixture on a warmed up engine all speed ranges. Normally a rack adjustment or baro compensator shim adjustment, idle mixture thumb screw adjustment or intake air screw will be sufficient. Internal adjustment of the pairs of governor screws is a fine tweek, but not normally needed. Lastly adjust the WRD for cold running. Add or remove oval shims to adjust fuel mixture during warm up period. Changing pin length will also alter the fuel mixture during warm-up, however you may wrongly change the shut-off temperature of the cold engine idle air.
There is a compound shaped cam inside the injection pump governor unit which develops wear grooves over time. This cam moves the rack depending on engine rpm. If the cam is badly worn, all these injection pump adjustments can compensate to an extent, but may not be able to solve every issue perfectly. .