Got a call back from the dealer. The car was no longer in "limp" mode, couldn't be replicated and hadn't thrown any fault codes. BMW engineers in Munich had them run some tests and send the data back. They've instructed the dealer to replace the Low Pressure Exhaust Recirculation Actuator. The part has to come from Germany so I won't have the car back until Monday to confirm it worked. I'll keep everyone posted.