Hey, I have a fairly new JK 15(2500 miles).My car while accelerating feels good and no issues or when not pressing the gas and letting it cruise. Now while on cruise control or I'm just pressing it down to maintain speed when rpm stays below 2000 it starts feeling like the car is jerking. Its only noticeable highway driving in speeds over 40+. I have 3.21 gears w/ 35 inch tires and recently had an aftermarket dynomax dual axle back exhaust installed. What could be the issue gears, exhaust , or something completely different?