Complex sentence: Even though the valve cover on this engine is black, it is referred to as "Grey Top" due to the grey intake plenum, to differentiate it from the fifth-generation Dual-VVTi "Black Top" in the Altezza.
Split into simpler sentences: Even though the valve cover on this engine is black, it is referred to as the "Grey Top", taking it's name from the grey intake plenum colouring. This naming is as such to differentiate it from the fifth-generation Dual-VVTi "Black Top" in the Altezza.