Welcome.
The 94 you have has flappers in the exhaust down tubes.
They're supposed to stop water from backing up into the exhaust manifolds when you slow down.
IF??? The motors overheated or they just fell apart???
They could have dropped down into the exhaust bellows and stopped at the drive???
They stopped putting them in the newer models.
Take the drive off and check the bellows and hoses for the pieces that might have fell in there and blocked the exhaust off.
No there? Then the next step is see if they are in the system at all.
Remove the exhaust bellows at the riser or remove the manifold.
See if they are in the down tube.
Get a factory manual and
http://volvopentastore.com/ has the parts diagrams for most Volvo apps.
Remember water and air follows the path of last resistance and there might not be a problem.