[Bob In Ct]

This is not a timing issue or both sides would be glowing. Since you have a single plane manifold I would have to think that the drivers side is running leaner than the passenger side. I'm no carburator expert but it sounds like a jetting issue. At 2000 RPM I would not think it's related to idle mixture (but who knows).

Do you have a PCV connected to one side (driver's side) of the manifold? If so connect to the base of the carburator.

Bob