I am having the exact same problem and I also have about 130k on the car. When I last checked the codes, it came up as P0420 which is catalyst below threshold (bank 1) and P0302 which is misfire in cylinder #2. I replaced the spark plug, O2 sensor, spark plug wire and fuel injector and cleaned the other injectors. It still does the same thing. Let me know if you figure anything out.