A few weeks back I was having misfire issues. I replaced the plugs with Bosch Plat +4 and haven't had the issue until today. At the time I also did an induction cleaning. I have blue STI wires, it is an '01 with 116K. The misfire was on cylinder 5 and I also got a P0154 code this time, O2 sensor. I am not sure when the O2 sensors were last replaced, my guess is they haven't. Should I start with O2 sensors? The plug wires look to be in good shape.

Any suggestions appreciated.

It has also been a quick misfire that only lasted a second, never consistent.