My 07 Cobalt is about to hit the 100,000 mile mark on it's 2.2L motor. I've read a lot about the timing chain needing to be replaced about now. My question, can I change out the tennsioner and not change out the chain? Or is it best to go ahead and change both out with this many miles? I understand there is an updated tennsioner that should replace the existing one. Apologies if this has been asked already. I couldn't find anything to answer this question..