This is my first rodeo with detailed attention to fuel injection. So be kind!

1. Why are the aftermarket rail to distribution block return hoses so large a diameter?
The return to tank outlet from the regulator is so small by comparison. Which makes sense.

2. If the spec is for, say,45 psi fuel rail pressure, controlled by the regulator: What is the purpose of the vacuum hose connection to the regulator? Does it over-ride the "normal" and open the regulator when the manifold vacuum is high?

3.Is the small port in the distribution block for a pressure gauge?

Thanks