While traveling at highway speeds between 65-75MPH the vehicle with violently shake while shifting and then lunge forward. However, during the shaking the vehicle is hard to control and feels like it is going to just shut off. This scenario primarily happens on flat roads at the above mentioned speed. However, we have noticed an issue with the vehicle while turning corners and accelerating, as well as, when going up hills or steep highway sections. The vehicle has a V6 but seems to struggle shifting when trying to accelerate even to 40-50MPH. In some instances the vehicle has labored up a hill and seemingly dsn’t want to downshift and pick go faster. It seems that this issue has triggered a TSB from Kia, but the issue has potential for elevated risks for other drivers on the road. If the vehicle is unable to maintain freeway speeds or climbing speed, then it poses a risk to traffic on either side of the road and the potential need to pull over. It seems that the vehicle loses power or momentum and would make it very dangerous to get off the road or onto the shoulder. The violent shaking could cause a driver to panic and lose control of the vehicle while at highway speeds and needs to be investigated.