Filtering power to stepper motor drivers for EMI
So, what do you guys use to make your steppers to behave to meet CLASS
  B?


I use a closed frame (faraday shield) with filters on the power to meet class B. If the motor cables need to go outside the frame, I use shielded cable.

One thing that may be an advantage to knock out 100Mhz+ signals is to short them out with capacitors. X2Y capacitors are multiterminal devices that cut the ESL in half and are effective in the GHz range. I also use them for low noise applications on analog electronics. They may be useful to dispense with the inductor an use only capacitors to short out high frequency noise that arises from high frequency sources.