I only have an AFC Neo for tuning.
Hmm This statement below seems counter intuitive. For cold start you would want higher vac/ thus higher fuel pressure, correct? And Hot you would want it blocked to go to lowest base pressure?
I did find this:
http://members.shaw.ca/dsm.1000q/Eng.../solenoids.htm
"The right-most solenoid, marked with a green arrow, is the fuel pressure solenoid. This solenoid allows the engine control computer to temporarily raise the fuel pressure for hot starting purposes. This is accomplished by cutting off the vacuum hose going to the fuel pressure regulator. It is not used for anything else, but it can provide a useful tap-in point for a boost gauge, since the regulator "sees" the intake manifold pressure. (If you tapped your boost gauge in here, but it doesn't read any vacuum right after warm or hot starts, you probably connected to the wrong side of the solenoid.) "