hmm...first off...i would reccomend against the taking out of the exhaust manifold. very difficult job that would yield nothing in the field of cleaning. The intake manifold is a good idea if you have the time and such. Perhaps a better way of cleaning it is to use a manifold cleaner where you don't need to take the whole thing off. Manufacturers make products such as sea foam intake cleaner and bg 44 has stuff on that level as well. This would probably be a better idea in my opinion.

you can clean the actual engine bay by using basic engine degreaser and then going over the bay with a metal or soft bristle toothbrush...either way. At this same time you can replace vacuum hoses if necessary and such.

FOr carboned valves i would reccomend either the water through intake method or the use of products made specifically to be used through a gas tank such as techron, redline si, or bg44k. The water through intake method involves the disconnection of a vac line, through which water is fed whilel revving the engine a bit...this water works like a steam cleaner and blows all the gunk off.
Plenty of ways to get gunk and carbon off valves and things...a search on the brickboard will find you plenty.


have fun:)