High Idle when engine is warmed up while in park

I have a 89 ford probe gt, when I turn my engine over and it warms up it idles between 1500-2000 rpms if I drive it for a little bit it ends up dropping back down 750, but itll still rev up to 1500-2000 rpms randomly and them stop and go back down to 750. I dont know if its the IAC valve or if its my throttle position sensor. I have checked some of my vacuum lines and from what I see there arent any leaks. Should I adjust my valves? Or what? Im in the process of replace the valve cover gasket and oil pan gasket and timing belt cover gasket as well as the crankshaft seal. Will any of these things help my idle lower?