Are your valve seals shot yet? Don't fix what isn't broken unless you know it's going to be soon.
Do the basics: Belt, transmission fluid, check the differential fluid, make sure any bearings are all right, check for gaskets and gasket leaks, flush and fill the radiator, new air filter, new fuel filter, maybe get new O2 sensors? Just all the basics you should be keeping an eye on. I think the weak part of these motors are the valve seals and oil consumption tendency; everything else is pretty sturdy in there.
Clean the secondaries or whatever, butterflies, they're disgusting.