If the problem you are trying to solve only involves one of the four cylinders, I don't see how a carb would be to blame.
I wonder if it's possible that an intake valve might be sticking in #1 cylinder. Seems like if were failing to completly close, gas would not only be sucked in on the intake down stroke but also on the power down stroke. At idle speed the cylinder might be too cold to handle the excess fuel.
What you think..just a theory ?
A low compression reading might give a clue as would a Vacuum Gauge although the Vacuum Gauge will not pin point the exact cylinder, just the condition in general. I'm not familar with the TR3 intake manifold so a vacuum gauge might not be possible ..too bad if it's not