If you have an audible leak this will be your culprit. You can rig a pressure test for yourself to check. But if you hear a leak I would change that out first.Air filter has 58k miles on it. I just ordered another one. Fuel filters get changed every 13k miles with regular service. The cummins dealer said they heard air leaking from my CAC when the truck was on their dyno but that was back in June. I bought the truck the end of February of this year. I started noticing a drop in power a bit. Actually I didn't notice much difference after it was turned up.