[Kenth]

1966 center carbs uses the vented gasket #7015106.

Delco Rochester Bulletin 9C-627 Date: May, 1967 (1966 389 Tripower) calls for the non-vented Throttle Body gasket #7015345 in end carbs.
Same gasket used on ALL 1959-66 Pontiac Tripower end carbs.

In older Bulletins dated December 1965 ALL 1959-66 end carbs used the vented #7015106 gasket

In Bulletins dated May 1967 ALL 1957-58 Tripower carbs and ALL 1959-65 center Tripower carbs w/o HIC uses vented gasket #7015148.
1959-65 center carbs w/HIC uses vented gasket #7013680.

In older Bulletins Dated 1957 all 1957-58 Tripower carbs uses non-vented gasket #7011326.

I have found using gaskets in the revised bulletins will work best.

FWIW