Well, if you want to go all-out, then you can drain all your fluids and do flushes (tranny, coolant, etc.). Of course change all your filters, including your fuel filter, change your spark plugs if you haven't done them recently, etc. If you want to clean your engine manifolds it won't hurt, there are some good how-to's on here about taking the upper and lower intake manifolds off and cleaning them.
