My exhaust manifold just won’t seal up. I’ve been testing for leaks with the engine off by using a vacuum blower pushing air into the tailpipe, and then spraying the exhaust with soapy water and checking for bubbles. I see bubbles all along the top of the manifold and along the bottom on the spots where I am able to spray the soapy water. It's a new manifold, a Dorman, had to replace the old because it was cracked. Should I just keep tightening the nuts on the manifold studs? The book says 16 to 19 ft. lbs but that doesn’t seem very tight. I tightened them to 22 last night just to see if it made any difference but still no seal. My only guess as to why this is happening is that the studs/nuts are not applying enough pressure to crush the gasket and air is pushing past. So is the only solution to tighten further? Or is there danger that as the metals expand at different rates it could cause more issues? Beyond tightening it more, the only other thing I can think of would be using copper rtv to seal it, but I’m not sure how well that would hold up long term. I did recently install a remanned cylinder head, but given that the leaks are basically around the entire manifold I don’t think head warpage at the manifold mating surface would be the issue, and I did check the manifold itself for flatness and it was fine up to .004 of an inch. Any advice would be great. I’ve had the exhaust apart 4 times and this problem is killing me. I can smell fumes in the cabin while I’m driving and I get a check engine light code 172 running lean. Car is 93’ 1.9 liter.