When you blank them you leave the plugs connected ,you removed the pipes that feed back to the inlet side , then remove the butterfly so when the ECU tells the butterfly to close you don't blank of the inlet airflow , but the motor that turns the butterfly still works so the ECU thinks all is normal. Hope that makes sense ... you basically trick the ECU to think all is still connected except no exhaust gases can be recycled thru the engine.
If you were to un plug the EGR's my thoughts are it would fault straight away as the EGR would then not be working.
Cheers Ean

