I have a 94 3/4t Chevy Suburban 2wd, has 191k miles. When the c/c is on and when going downhill the cruise will rev up and down even when on a slight downhill. Also it has started when using the throttle with out c/c on. One has to apply then let off the throttle to maintain speed. Can't just let off just a little. Is it the throttle position sensor? FSD?

Thanks in advance!
WIPPdriver