2000 Chevy Venture fuel pressure regulator

I have a chevy venture van with 188000. Lately hard to start when cold out. Seems like no gas.I had the fuel system cleaned, change fuel filter and checked fuel pessure. It was around 42psi. The book says for my year should be between 51 and 57psi.I need to check to make sure the regulator is not leaking. What is the easiest way to do that or can I be missing something?Some other info on the highway when acclerating the car would shake then stop when you take your foot off the gas but that cleared up pretty much after the fuel system was cleaned.I'm hearing the fuel pump when sitting at an idle. The engine light is off.