I've used Permatex Ultra Black in the past. Never had a leak but every time I've replaced a gasket there is always a portion where it did not adhere and that always seems to be the case, no matter how clean I get the surface before application. I've also noticed that it does not seem to stick as well to aluminum. Still, never any leaks.
I've also used Permatex Permashield gasket dressing / sealant which is a tacky but non hardening product and no problems with that, either. It is a replacement for a product called Hylomar HPF, which is no longer available. I like this more than the silicone because , for one, it seams to work and disassembly and prep for a new gasket is much easier since it does not dry.
On intake gaskets, I've only applied silicone or sealant to the coolant passage. Also remember that some of the bolts need thread sealant.
Lawrenceville, GA