Sounds like Air-Intake problem.
Remove complete this guy
to have this in your hands and to take home and look accurate for fissure !
Strech every fin / rib !
if not help -> remove the throttle valve and make it clean ( idle bypass pipe )
if not help -> search with aliphatic volatile hydrogencarbonates for leaks (motor will do anything when you have leaks)
if not help -> change throttle valve potentiometer
if not help -> change the air mass flow meter
if not help -> change throttle valve completly
if not help -> Burn the xedos down