PCV to power brake port... The port on the carb, or on the booster? Is it T'd to connect both the brake booster and PCV into the carb base?
Unless someone modified your distributor to run on full manifold vacuum, your advance isn't working right. Try moving vac advance to the ported/timed fitting. Trans modulator wants full manifold vacuum.
Ported vs full manifold distributor advance is a discussion all it's own.

 

No, the brake port and pcv port are connected directly together with a hose. No t or anything.

 

When you say PCV port, are you talking about the vacuum port on the carb, or are you saying the PCV valve on the valve cover is connected to the brake booster?

 

I'm talking about the port on the carb.

 

That's better than what I was picturing! What kind of crankcase/valve cover venting do you have, running a pcv valve?

 

See attached