I have heard of people using the other (less expensive accumulator) with great success. The flowchart I have seen is from the factory service manual. It relates to pre-charge pressure. You need a set of brake gauges and you need to make an adapter. The adapter is a 1/4 NPT tee. It will have 2 female ports and one male port. Change female port on the top to M12x1.5 thread pitch. DONOT use a helicoil, use a time-sert, keen-sert or thread insert. The helicoil will leak. Order a hydraulic adapter to change the male port (directly oposite of the female port with the thread insert) from 1/4 NPT to male M12x1.5. Leave the other female port alone, this is the port used to attach the brake gauge. This adapter will allow you to remove the pressure switch, install the adapter, install the pressure switch on the adapter and connect a set of brakes gauges to the adapter. You can then hook the electrical connector back up to the pressure switch and check accumulator pre-charge pressure and pressure switch on time (using the specifications from the GM service manual). By the way, if your feeling really rich, you could order the factory GM tool from Kent-More ($479). The tool I'm using cost approximately $130. Ordered a set of brake gauges from Harbor Freight tools for $93, adapters cost $8 (local hydraulic shop) and machine work was $20.
