If you are getting a slower feed through the nozzle, your extruder is slipping or your nozzle temperatures are too low. One of the methods I've seen for setting e-steps is to make a mark on the filament (direct drive) upstream of the entry point to the extruder, with a frame reference to determine starting point. Make a mark 100 mm farther away from the first. Command the 100 mm feed. If it's incorrect, adjust as needed. In your case, I'd suggest to ensure there is no slipping and that temperatures are correct.