Yamabond is very good stuff. A bit expensive, and it definitely has a shelf life once the tube is opened, but unlike regular silicone it doesn't leave 'strings' of sealer around joints. It 'flows' onto the adjacent surfaces instead. The only downside is it's a bit runny and won't fill big gaps (like end seals on intakes). I use it in lieu of gaskets a lot, and haven't had any sealing issues with it.