I agree and im replacing XP controller with Kuteng 500w controler.
New controller will increase speed by 2 maybe 3mph but im not going for extra speed because 28mph is more then good for me on this bike.
Sine wave controllers are more stable, high efficiency, and have low current consumption plus this controller has exrta speed sensor wire so i can mount magnet on spokes and have external speed sensor in case motor internal speed sensor will still show wrong values with new controller.
I will also be able to hit 28mph+ with throttle only.
I have no idea who makes XP controller.
Next upgrade will be 20Ah battery so i can get range around 100miles