cis imo is simple theres fuel going through the tank then the fuel pump then the accumulator to the fuel filter in to the fuel distributor then vacume from a the fuel plate(i call it) whitch is in the air box raises and with vacume from the engine opens the fuel distributor and sends fuel to the injector. the common problems with this setup is the fuel plate gets dirty or little criters get in there.
if you know any of us older vw guys we most likly have alot of cis systems if u need a hand let me know. o and another thing that goes bad with these is the ignition part behind the key most of the time from moisture from bad seals from the roof. check for water and take a close look around windows