a fuel press gauge rented from one of them parts stores would do the trick, I think. If you have a regulator on it, I assume you can dial it in to 3 - 4psi. Personally, if you're running an SU fuel pump, I would check those float levels in the carbs, and make sure that needle valve is stopping the fuel flow when it should.
Just because it's new don't mean it's working the way it should.