Fort Knox,
When you have the intake/exhaust combination off, lay something relatively flat across the face of the manifolds...a aluminum yardstick or such!
It is not uncommon for the exhaust to warp and cause gasket sealing problems. You probably want to get this job done 'real fast' but unless you do it right, it will be 'half fast'.
If it is not obviously warped, just re-gasket it.
Stuart
