I ordered a new compressor, this model. I was told all units now are 4 piston and 4 stage, like the video. My manual has pics and breakdown of a 4 piston unit, but mine is not. This unit is only a 3 piston, 3 stage unit? Looking at it with motor on the rt and pump on left, I have pistons at 12, 6, and 9 o'clock. The 3 o'clock side of pump is flat. Am I missing something?