I have owned this car from new and it currently has 32k miles. The only fuel used has been 85 octane or occasionally a tank of 93 octane. There is a distinct hesitation when accelerating from speeds of 10 to 15 mph and I do not believe it is due to the transmission shifting. I did move to my current state,California, from Pennsylvania and was told by my local Hyundai dealer service department that because California has a different gasoline formulation from most other states as well as a summer and winter blend to reduce emissions it is recommended to run a bottle of injector cleaner every 15k miles.
Any feedback is appreciated along with suggestions as to which brand additive might be best. I have a bottle of Chevron but have also read Amsol and Lucas are quality products.