[Jacksonlll]

You probably have a small intake air leak. File the intake manifold flat. Clean it up until it is all shiny. Do the same thing with your carb flange, then use a new gasket. That small air leak is enough to lean out the system at a time when the fuel is pushed forward causing a little less fuel in the jets. This can also be caused by an air leak anywhere in the intake. Manifold or vacuum line.
Use a mirror and light and file the manifold flange while still on the car. Easy fix.