Fuel System Questions?? parts and what they do?

[gabel@acmepower.com (Glen Abel)]

     Ok, 86 5K TQ 
     
     there is on the back of  the FD a unit that looks like a mushroom with 
     fuel lines coming and going, could not find it in the Bentley book, 
     What does this guy do for a living?
     
     
     The Pressure regulator, on the block (2lines) how does it work? are 
     there common failure modes?
     
     Plastic valve (bypass) I biased it up out of the car, put vacuum to it 
     and It worked... Does it get its signal from the Throttle switch? I 
     would assume that is does, switch closes, biases up the valve .. valve 
     opens... idle drops.... (shift gears) back on throttle.... valve 
     closes.  
     
     Are there rebuild kit for the FD?   
     
     What holds fuel pressure at the injectors?
     
     there has to be check valves in the fd itself... maybe not but  things 
     are looking weird, what's Robert Bosch'es Phone #er?   
     
     Anyway .. today was the first day of real snow and I drove the Quattro 
     for the first time.... 1 word AWESOME.. Esp Diff locks!!! 
     
     Gabel@acmepower.com  
     
     Thanks   Glen...