2.2 x type misfire

had a x type 2.2 since new dec 05 i have had it t jaguar 32 times over that period, with the sme thing, they have had every expert under the sun to look at it and changed many parts. the problem that i have had since month two, is that the car starts to jerk when it gets to a certain amount of revs as if you are in the wrong gear and the car is about to stall. i also want to know whether i can reject the car at this late stage as the problems is still ongoing robert