Hello. We are currently dealing with a problem on a cylinder head of a Mitsu 4G63 engine on a CAT GP25. We are ready to rebuild the head but cannot find the part number for a 3rd valve and it's seal that works alongside the exhaust valve. Apparently this 3rd valve is for gas recirculation, but CAT dealer cannot identify it. Does anyone know the part number for this valve and its seal?

Thanks,
OB1