On reading the citroen technical forum where other people have had the same problem a few people have said the brake light switch tells the fuel system it's braking and to stem the flow of fuel hence causing stuttering power if the switch is faulty, now i don't know as i'm not a mechanic,but i've recently lost my job and can't afford to take it in to garage for a diagnostic check,but i'll take any advice and help i can get to resolve this problem, it may just be a process of elimination.no fault lights on the dash