What is your vaccuum at an idle in gear?
The purple shaft 474 is getting to that range that it has enough duration that would cause lower vacuum especially in an automatic car.
With that said, what power valve is in it? Power valves will hang open if its rating is to close to your idle vacuum creating stupid rich at an idle.
You can also try decreasing your shooter size. The large shooters can sometimes bleed fuel at a higher than normal idle.
