Nobody sells exact replacement controllers except the major bike brands that have a warranty reputation to maintain.
You've got a 25 A 48 v controller with the black in-line connectors. I have been unable to find a replacement controller with those connectors in the US. The market has moved on to round "juli" connectors. You might be able to get someone in Hong Kong to find one for you with those connectors (em3ev.com), but if somebody hacks your debit/credit card from HK where you made the purchase the FBI won't help you. I did find a controller with white rectangular connectors, which connectors can be bought in an unassembled pack on e-bay. I cut the black connectors off my pas pickup, throttle, hall effect sensors, soldered on white ones, and went with a 10 A 48 v controller. Wimpy, but when Shanghai was shut down for covid that was all that was available in the US. Inventory may be better now. Be aware "scooter" controllers, which was all I could find in the US, require a 48 v signal to the "door switch" input to do anything but sit there. The controller stays powered up with the "door switch" on and I wasted 2 v of battery charge when I left it on all night once.
25a controller is pretty high power so if full throttle start (is there one?) is not fast enough, not much chance of increasing acceleration. That much power at 48 v is illegal now in ~40 states. 750 w limit. If PAS is accelerating slowly then a programmable controller like a KT might do better. 20" wheel is a programmable parameter on many models, so a controller you can program with the display would be useful.
One thing that really increases acceleration from a stop is more winding poles. Quickest geared hub motor I've ridden is a Cutler Mac12t 1000 w 48 v. 12 poles instead of 10 for faster peaking torque curve. Would only go 23 mph with 26" wheels, but that is faster than I ride on the flats anyway. Nobody is selling these in the US anymore either.
