The misfire that your feeling might be the PCM pulling back timing because its seeing an issue with a knock sensor.
Unless its because your going up hill and the strain on the engine is causing a chatter that the knock sensor is picking up, but that still doesn't account for the P0325 because that'* a knock sensor failure code...
Unfortunately, the 3800 uses 2 knock sensors. One on either side of the engine block. The front sensor is easy to get to, but the rear sensor is a pain because the transmission sits right next to it. Which is another dilemma. The wiring for the oil pressure sensor and the knock sensor, sits right next to the passenger side driveshaft. I wonder if a wire has rubbed on it. BTW, its only a single wire going to each knock sensor.