Marlin - Micro stepping Slowing down speed.

Hey guys I am a long time looker on this site. I have been playing with micro stepping and when I change the drive for micro stepping per the jumpers and then change the line in marlin to
#define DEFAULT_AXIS_STEPS_PER_UNIT {157.48, 157.48, 157.48, 47.14} vs 78.74 per my drives
It will slow down my speed of travel. If I microstep even more it slows the travel even more. is there more settings I need to change?
Thanks everyone for your help!!!

What speed are you trying to drive them at? There's a limit to how fast marlin can drive the motors (although I don't know what it is yet!) and you may be hitting that limit