Hello! my first posting. working on a 91 new yorker salon 3.3l--when revving engine speedometer needle moves like a tach needle.will actually add mileage to the odometer.1 mile added in just a couple minutes of revving.--while driving the speedometer fluctuates and affects performance as needle moves. car does not have a tach.think it is problem with v.s.s.? help! 9:40 pm 8/14/2006 thanks!