Most new cars have what they call break in oil. If I were you I would use full synthetic oil. I use mobil 1 but everyone has their own oil they use. Also there is a T.S.B. on aftermarket oil filter restricting oil flow through the filter causing engine knock and loss of power.
I used a K&N oil filter when i did my first oil change. It runs like a champ. Hopefully you can narrow it down to what is causing the problem
Since new, I've used whatever filter and oil (non synthetic) that the Hyundai dealer uses, in my 2006 Hyundai Sonata. It also runs like a champ. I did the same for my wife's 2006 Tucson, 2007 Santa Fe, and now the 2013 SFS (yes, she's had 3 cars while I'm still driving the one

).
Aside from cost, does it really make a difference whether you use the standard oil and filter the dealer provides, vs. a, for lack of a better word,
premium oil and filter? Can you feel the difference when driving?
John