Diagnosing a Cracked Intake/Exhaust Manifold

>Does anyone here have any experience in diagnosing a cracked
>exhaust/intake manifold on a 4.0?  I noticed a couple of
>weeks ago that my exhaust note changed at idle (seemed a bit
>louder), and that the whole exhaust assembly aft of the
>downpipe/cat junction was vibrating heavily (the downpipe
>was held pretty firmly in place).   Now, I've been hearing
>rapping kind of sound from the engine compartment; sorta
>like stuck lifters.  It's been getting louder, and
>definitely more prominent under load.  However, the engine
>still appears to be making good power.  I'm thinking it is
>the exhaust manifold (maybe sorta hoping, as I've been
>wanting to put in a Borla); just wanted to check how to be
>certain before going ahead and convincing the wife.....

The easiest way to spot the crack is to raise the vehicle on
a hoist and use a mirror to look down at the manifold where
the back two pipes join in to the rest, that's where they
crack. Another method is to start the Jeep cold and reach up
from underneath to the same spot and feel the leak. If you
pull it out it can be welded easily.

 Dave Burns