I changed the ait filter in my wifes envoy bout 3 weeks ago. And ever since then she keeps tellin me shes hearing this medium-high whining noise when she accelerates. So i checked all the screws for the filter box and they are all snug, dont feel any leaks. So i took it for a drive and sure enough when you accelerate it makes this whining noise. No noise when idle, and it goes with the engine, like if your slowing down not pressing the brake, just coasting you can hear it whine down also. Anyone know what it is? We just lost the factory warrenty and we are leaving in 3 weeks to drive from AZ to MI.