can any one help please a good friend of mine has a problem with here fiesta st its on a 05 plate iv not sean the car yet but wot she should its doing is when she pulls up the revs drop to about 400rpm then go back up to about 11,000 then back down and some times it cuts out but it drives ok when going along its just when she pulls up that it starts to hunt .can any one put any light on this matter please