Any idea what this could be on my 2001 Ford Focus SE?

White idling at a light there's a "shudder" of sorts and the car feels like it is going to stall… I recently had a new fuel pump put on but that has not fixed this.

This could be your o2 sensor.

Pull the OBD2 trouble codes and work on troubleshooting the parts pointed out by the code. Try to not discard good parts.

Clean the throttle body with throttle body cleaner spray. If that doesn't help you need to have the idle air control motor inspected.