I know you don't want to believe it, but the mechanical pump will cause the problems you are having, and a reg won't fix it. The Weber is too sensitive to the pulsation of the mechanical pump because of its close proximity to the carb. If your pump is only putting out 3-4 psi, it is almost dead, as a new pump puts out 9-13 PSI. I have run Webers for over 30 years, and installed them on several trucks - if you want the rest of the issues to go away, go with an electric pump - you won't regret it.