I have one and have just compiled the TH3D's marlin 2 firmware for it.
I uncommented the
and set the steps to 2700 as per the Zesty documentation
#define TITAN_EXTRUDER_STEPS 2700
Using the Titan extruder entry also sets the correct direction for the extruder stepper. If I use CUSTOM_ESTEPS the stepper moves in the opposite direction.
I know I'll have to reduce the stepper motor vref to 0.3V before I can run any tests. Hopefully I'll have time tomorrow.