whosurpopi

Its an auto, and I recently replaced the plugs and coils. It was running rough (especially when the air was on) but the plugs and coil fixed that. Now it runs very smooth, until it shifts into 3rd gear. Then the whole time im giving it gas, the car is hesitating even through 4th gear. When I let off the gas, it seems smooth. It also kind of shutters right before it changes gears into 3rd and 4th. I am thinking torque converter, but maybe just a flush? It just turned 100k. We have only owned it for the last 4k miles.