I presume you are referring to the manifold bolts. Just mix 50% acetone and 50% automatic transmission fluid and hit the bolts with the mixture for a few days and they will readily unscrew. Give each bolt a shot every morning and every evening for three days and the corrosion will dissolve.
Also, use good six point sockets so you do not strip the heads if they have rusted badly. Twelve point sockets will round bolt head corners if they are already damaged.