Z Axis issues after leadscrew conversion

I have an issue that has me flummoxed.

I have a Maker Farm Pegasus 12 where I upgraded the M5 threaded rods with a 0.8mm pitch to M8 leadscrews with a 2mm pitch.

Using the Prusa calculator I determined that the zsteps/mm should be 1600 (200 steps, 1/16 microsteps, 2mm pitch). I then updated the Marlin 1.0.2 firmware for the appropriate setting from 4000 to 1600 as follows:
#define DEFAULT_AXIS_STEPS_PER_UNIT {80.19,80.19,1600,90}

Unfortunately, my z axis is out of wack. It is like at least 4x what it should be.

I checked my RAMPS board and MS1, MS2 and MS3 are all closed so that means that the microsteps should be 1/32 but I suspect somewhere else it is forcing it to 1/16.

Any thoughts on where else I might look? Other options would be to contact Colin from Maker Farm or just keep dialing down the zsteps/mm but it seems like it should be 1600.

Thanks in advance.