While getting my convertor replaced at the dealer, they informed me that these 2 coils are failing. They have not thrown codes yet, but after having killed my convertor from a misfire in #2 cylinder, I want to get this out of the way ASAP. I have an '06 CTS - 3.6l. My question is - is it possible to change these 2 coils without removing the upper manifold? Thanks.