Check the fuel line near the floor I had a police car that was sucking air threw porosity in the line changed the hose back at the tank and problem solved As stated check your fuel pressure but be careful air will pressurize and possibly give you a false reading if you pump is good Also on that model carb check your metering rods they can be set wrong and causing some of that problem. It is easy to work on carb so why ditch it? one ;last thing if you are reading over 20-21 inches of vacuum its too lean and hence part of your problem