From 1973.5 until 1984, Porsche's primary fuel injection system, made by Bosch, was known as CIS (continuous injection system). There are a handful of people left that really understand the intricacies of the system so most owners are talked into carburetors or another form of fuel injection when their engine exhibits hard starting, poor idle, or rough running. Bosch designed and sold this system to almost all of the major European auto manufacturers including Porsche, Ferarri, Mercedes, Audi and others. Each system has a few differences and it is quite a task to try to keep up with them. But the basics of fuel management still apply... how much air is going in determines how much gas gets pushed through the injectors.
There are a few basic elements that make up the CIS fuel injection system: fuel pump, fuel distributor, warm up regulator, injectors and the auxillary air valve (AAV). I've taken apart and rebuilt most of these except for the AAV. Today I had a bad AAV in my hands and decided to see whats inside. Check out the video to see the hardware.