So I have a missfire issue. Just recently bought the car for work because of reliability and gas mileage. I was on my way to work this morning and I could tell the power decreased a little. Well I noticed the check engine light was flashing and I was around 3500 rpms so I shifted to 5th and got the rpms down and was on a flat and it stopped flashing and went away. Well when I went to go up another mtn I geared back down and rpms around 3500 or so and it started flashing again. But then went away again. Gonna change spark plugs this evening and see if I can pull anything up with my code reader and potentially change a coil pack if it's just 1 cylinder misfiring. But should I check into changing the cat? It has 166k miles