I would only put the factory recommended ac plugs in it. After speaking with my professor and a few GM techs they said that they usually only see coil pack issues when there are not stock plugs in it. I know that it has been debated here before, so no jumping down my throat folks. They all said that the system was designed for the resistance that the AC plugs provide. Although aftermarket companies may make plugs made out of the same materials, they are made for a wide range of vehicles not just GM, so their resistance may not be within the spec that the system was designed for.