My grey matter is a bit dull but I seem to recall a method where one started and heated up the manifolds to soak then took iced water that's at its coldest, maybe with a bit of salt in there for a lower temp, with that being splashed on the manifold/nuts/bolts to break them loose.
I have plans for a set of long tubes, high flow cats, and a pair to the rear out the stock pipes via local shop because I don't have the patience to do it myself. ;-)
I have a standing quote for about $3,500CA all-in which is pretty reasonable considering all of the grief I remember from my youth where buddies and their manifolds were sitting on the driveway with tears because there were broken studs still stuck in the heads. ;-)