That your motor's weak... . Of course you already knew that, but it's just another indicator.

13in hg is very low, especially with the idle set at 1000. A street-ported TII with good compression would pull around 15-17in hg at a normal 750RPM idle IIRC.

How many miles on your rebuild?

Also, how many (original) miles on the rotor housings that you re-used?

I'd consider another "rebuild" with fresh rotor housings, apex seals and coolant seals. If all the other seals were replaced (as well as their respective springs) during your recent rebuild, they should be reusable in your "new" motor. IF you decide to rebuild of course.

BTW, who did the rebuild?

 

I have no idea who did it or how they did it...trying to find out.