tearinghair, I take it there was no problem prior to you getting their plugs changed? where the plugs checked for cracks in the body? take them out & check, have the plug leads been put on in the right order? with respect to answer, the plugs are normally set to the car they are bought for its not that often they are out, if the car was right before the plug change then its up to the garage to put it right, do not be fobbed if they say its this & that, explain the car was right before the changed what you have stated.