This is an exquisitely designed (appears very simple,but is not) fuel distributor. Here is the problem--the unit has to feed each injector the identical fraction of the total fuel flow over the entire range of total fuel flow--from less than 1 gal/hr to over 50 GPH. To accomplish this, each 'metering assembly' has to achieve the same pressure drop as all the others over the flow range. (All this assuming each injector has the identical flow characteristics as well.)

This entails adjusting ALL the metering assemblies so the base pressure drop and the running pressure drops for each assembly all follow the same curve--flowing the identical amount of more fuel as the pressure increases. The CIS adjusts fuel flow with a 'mechanical/hydraulic' link bewteen air flow (the saucer plate in the intake horn senses air flow) that raises the fuel pressure to the fuel distributor as air flow increases. This requires that each piston and spring have the identical force vs displacement characteristic and that each piston have the same 'drag' in its bore,etc., etc.

Each and every part,component, and adjustment HAS to be perfect for this to work. They do-when new and clean. They do -not when they get trash and fuel gum in them or the O-rings are destroyed by ethanol or MTBE in th efuel or harsh 'injector cleaner' solvents. Also any fuel injector that is no longer on its original flow vs pressure curve will cause low or high fuel flow to that cylinder.

Theoretically, you CAN adjust each metering assembly to closely match the flow characteristics of each particular injector. Has to be done on a very expensive 'flow bench' and takes lots of time. Benefits are very marginal IF all thw injectors are within OEM specs. Since these injectors are cheap, (compared to electronic ones), its more cost effective to bench clean or buy new ones than try to adjust the fuel distributor.

Adjusting the fuel distributor is NOT a job for a DIY--even if you ARE highly skilled in other areas. Without the very precise,accurrate, and $$costly fuel flow test equipment, you have no possible way to adjust the fuel flow metering assemblies as required to achieve the balanced flows needed.

This is why everyone migrated to electronically controlled fuel injection--it simply was not possible to achieve the precisely identical fuel flows (fuel-air ratio)required for the 3-way oxidation catalyst systems to function properly.