geminiford

Hi everyone!
Please can someone help me! My car loses power intermittently, it feels like she is holding back, then it rectifies itself and I shoot forward. Also she intermittently stalls if I dont keep the revs up. So far this year I have had the plugs changed, fuel filter changed, coil changed and oil and filter changed. Can there be more than one coil? If not what ever is wrong with the car? The mechanic cannot diagnose the problem until he sees it for himself, and as the problem is intermittent this is proving tricky! Suggestions please!

Thank you!