Quick question about the FPS

[-D-S-M-]

I've searched the forums but I couldn't find any topics that look like they have anything to do with what I'm asking. I am not asking for you to post a link or say search again, I would just like a simple answer.

On the back of the FPS (1g 1993 TSi) there is what looks to be an adjustment knob. What does this knob do and what will it change? Fuel pressure?

 

[jeffo]

If you are referring to the FPR solenoid, that is not a knob. It is a vent cap, with a filter inside to keep dust from being sucked into the FPR when it is energized.
keydiver