So I noticed an easy way to tell what orientation your chopper wheel is when you do the 300zx ecu swap. Notice the attached picture, how there is a circle punched in by the top piece? It competes the notched out space in the CAS, that indicates the top. The bottom doesn't have anything that could punch out a circle. Just a thought. (Yes, I know the pictured chopper wheel is a 280zx wheel, I just installed mine)