Check the mating surfaces to make sure they are flat. If the gasket surface of the manifold is eroded or otherwise damaged, have it milled flat.

If you look inside the exhaust manifold you will see a machined seat for the lead pipe that Eric mentioned. (If the manifold is on the car, you can feel it your finger.) If you have the manifold milled flat, make sure that seat is re-cut to the proper depth.

Start with a new down pipe from Volvo as Eric indicated and use new studs and nuts. Good luck and let us know when that thing gets quiet. ;-)

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Mr. Shannon DeWolfe -- I've taken to using mister because my name misleads folks on the WWW. I am a 53 year old fat man. ;-)