155k on my SRT6 and had a similar issue. Replaced the O2 sensors, plugs and coil packs and its gone. Some of the findings from my time working on the car.

1. Pug wear was excessive in the front passenger cyl with one plug tip completely burned down. Most of the other plugs were anywhere from good to poor after 75k on them. Two of the coil packs had severe corrosion on the underside traces that look like they contact the engine when screwed down. After having to replace the rear O2 due to the front cats burning up, I replaced both main O2 sensors.

2. Ensure you are keeping the oil level at the recommended level and keep it clean. I have always felt a slight drop in performance at 3500k on an oil change. the closet I get to 7k the more I notice a difference and when I check the filters they seem to have collapsed so now I swap filters at 3500 miles and oil at 7k