'07 Hyundai Elantra | Barely Audible Noises

Over the last ~2 weeks “Shiny” has felt/sounded like it has to work a little bit harder to accelerate (mostly by making more noise than usual and not feeling like it has quite as much get-up-and-go in stop-and-go traffic). This kind of sounds like it did when the tires were really out of alignment, however the car drives straight on flat road.



Another thing that started around the same time is a barely audible high-pitched whining sound that happens during deceleration. It only makes the noise when I slow down, so it might not be a “final drive whine.” It doesn’t sound or feel like it’s related to the breaks. The sound is so quiet it can be covered up by heavy traffic or rain.



Shiny has ~60,250 miles. When we bought it in October 2010 Shiny had ~58,000 with new fluids and new tires.



Do you have any ideas what these noises could be?