[Hucky]

Is the bolt,

Stripped
Sheared off
can you be more specific

Can you see any of the bolt extending past the exhaust manifold?
Is there enough room to get a right angle air drill in there and drill into the bolt and use an easy out to remove the stud? If so, make sure the motor is hot before doing this, then spray some penetrating oil onto the bolt to allow it to come out easier with an Easy Out.

If there is alot of threads sticking out past the manifold you can use 2 nuts onto it an use the nuts like a head and back it out.

Hope any of this helps

good luck