I had the exact same problem when I was putting regular gas in the car. Like an idiot I listened to dealer then read the forums and owners manual that states different. Once I switched to 91 octane it got much better, with only slight hesitation when extremely cold out. Then when i got an oil change with Mobil 1 car while using 91 octane it accelerates buttery smooth while at the lower speed with absolutely no stuttering or hesitation at all. Hope this helps.