At least the last bolt will have to be tightened at more than 18lbs, because like I said, at 18lbs, there was still a gap between the header and the manifold on that one... The only bolt I have overtightened now, is that last one, that is on the place of the broken one... Maybe if I tighten that one a little bit more, it will stop making the sound, I don't know
I'm thinking like that because, if there was a gap at 18lbs, then maybe I haven't fully closed it at the torque I have on it right now, maybe a little more would close it good.
I'm afraid that it will brake with time, but if I don't overtighten that bolt, then I have a big gap that lets all the air out...