Do any of those Permatex or so-calld RTV gasket
sealants need to be used when mounting a carburetor
on its pad on the intake manifold ?

My usual mechanic says no, the pad is a kind of fiber
material and is not supposed to have any sealant coated
on it. He said the pad will flex itself in place when the
nuts are tightened.

However, I think my carb might be leaking vacuum along
its mount. The engine idles normally when cold, but
goes very rough when it heats up. It doesn't appear to
be vapour lock.