The fuel pressure in any stock 12-22 ktm / Husky 250 -501 should be 50 - 52 psi.  This regulator raises it to 58-60 psi.  In any bike without an O2 sensor, this regulator will cause your bike to run richer by .5 A/F ratio at all RPM's.  On 2020-22 EXC/XCFW's, this regulator is a must for good fueling at high RPM's when used with the Booster Plug