The fuel pressure in any stock 12-21 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 casue your bike to run richer by .5 A/F ratio at all rpm's.  On 2020-21 EXC/XCFW's, this regulator is a must for good fueling at high rpm's when used with the Booster Plug