2006 K3500 135091mi

Replaced Master cylinder 10/15 47025 mi
Replaced Hydro booster 1/21 105444 mi
No codes or lights
Lately on soft stops just as I'm letting up on brake the ABS pulses and feels like it might not stop. Once in a while it does this on harder stops.

I'm thinking maybe front wheel sensor. Feels like its front right but that's just gut feeling. Is there any way to test sensors?
Or to check ABS system without a fancy computer? My code reared sees nothing at this time.