Good day. Looking for help with the following issue. Manifold vacuum is running at 14#'s and should be based on the elevation in Phoenix at 19#'s. Engine idles a little rough as it is missing. The idle speed and timing are set to specification. Have replaced all vacuum lines. Did have a couple of holes in the underside of the intake that I used muffler paste to fill that brought the vacuum up by the EGR Valve. My thought is I have more holes that I can't get to and it is time for a new used manifold as Nissan does not have them any more for my year. My car is a 1977 280z early edition. Any thoughts or suggestions would be greatly appreciated.