Ford Ranger 1992 4.0 standard. My idle to pulses when in gear either if iM driving or if I have the clutch in

When switching between gears the idle drops down to about 500 rpm and if I hold in the clutch in it starts to surge if it not like if im going to stop and I put it in neutral the revs stay high about 1500 rpm untill I come to a complete stop. I have cleaned the throttle body changed both spark plugs and wires and fuel filter and air filter