.
Something else to consider is that there is a mouse Nest or two up inside your exhaust system. What I have done in past is make sure the exhaust valve is open on the cylinder and blow compressed air into that cylinder.
This works a lot better with headers than it does with the factory manifolds because there's a chance with the factory manifold of when you blow the air through there if there's anything inside that manifold it can blow it into a different cylinder at that time. So the best thing to do in that case is to remove the manifold and check them. Believe me you do not want a burnt Mouse Nest inside your heads or exhaust.