manifold vaccum for vaccum advance ?'s

Well its got a brand new pcv valve already... i just put a brand new pcv valve in it a couple of weeks ago... And this is a magnum 360, but it is not fuel injected It is carburetated. When i took the intake manifold off the engine and out it back on there wasnt a gasket under the intake manifold? there was two gaskets that covered the sides and gasket part that covered the front and back and then i silconed all 4 corners.
Maybe this broken intake manifold stud is causing all the problems, thats the only thing i can think off, its mot likely a vaccum leak between the head and the intake but the leak is not visible to me because its under the intake where the broken intake stud is.
But still wanna find out if my valve guides are trashed,
Is there a way to find out if the valve guides are ruined? whats the easiest way to find out?