Cylinder #3 is misfiring pretty bad, and it started just a couple of days ago. It's a 2012 STi with 90,000 miles. No aggressive mods have been done, only a Cobb AP running Stage 1 91 octane. I have cleaned the MAF sensor, run injector cleaner through my fuel and reset the ECU. I think I probably need to bring it somewhere for further diagnosis. If it were your car, where would you take it? I have been OCD about maintenance on the car, but have never changed the fuel filter or the coil packs. I did the spark plugs at 67,000 (Denso IKH20 stock temperature, .040 gap). Thanks in advance!