Two engine builders have told me it's the best thing there is if you're trying to seal a tough intake. I had my manifold machined but after the fight I've had with it I want the best sealer I can find. hylomar is supposed to be good but it won't seal as big of gap as permatex 2, if someone has a better gap sealer I'm open to ideas, but this is the best gas proof one I'm aware of.