I had a problem like that and like john said check your grounds on the motor..Mine came of the tranny and i couldnt even get the car to go over 2k like janky1 said looked like i could not drive my car just kept sputering.. I would also check the seals under the valve cover on each spark plug..If one of those goes bad it will soak the spark plug with oil ,then when that cyl fires it burns the oil off..But it will do the samething your talking about will sputter at low rpms... Just trying to help out..leting you know my problems ive had..