P2111 - Citroen C-Crosser chuggs for a few seconds while driving and then normalises itself again.

Question

While driving the car chuggs for a few seconds and then returns to normal operation. This normally only happened once during each journey, however it is now happening several times in a journey.
My mechanic plugged his computer in and it threw up the code P2111 (EGR Throttle Position Copy Signal Throttle Blocked During Post Operation).
I am at a loss as to what the possible fault would be.
Can any one please assist?
Thanks,
DavyMcC