I am about to reinstall my exhaust manifold on a V6 Tacoma and I was contemplating the need for
gasket sealant. When the old one came off, it didn't look like it had any sealant so my guess is no. The only reason I could see it as useful is to keep it put over the studs on the cylinder head and from sliding off but I can really mount it on the exhaust itself. Understanding that gasket sealant here may be optional, I was also wondering if it ever came be undesirable and detrimental.
The manifolds also have a considerable amount of rust on them. Should I sand off or somehow else clean at least the mating surfaces?