Since the pulleys are the same number of teeth as each other, they don’t change the ratio between the motor shaft and the leadscrew as compared to stock (both stock and Dave’s new setup turn the leadscrew the same amount as the stepper shaft turns). I agree about re calibrating for tension, though.
Dave - If you happen to have some 1-2-3 blocks around, I recommend using them to get a super precise calibration: Precise Z Calibration Procedure