360 runs great one day and then poorly the next

I'm pretty sure there are some vacuum passages on the underside of the base plate on the TQ that need to be open to the manifold plenum to get a good signal. I tried running one once with a 4-hole gasket, didn't run quite right and I couldn't tune the idle, not to mention the throttle butterflies were touching the edges of the holes in the gasket so I couldn't open the throttle all the way. Swapped on an OE open-style gasket and it ran much better. It was on an Edelbrock Performer (non-RPM) intake though.

I later realized the 4-hole spread bore gaskets are meant for Quadrajets...