Hi guys I have a 2012 Civic SI with 160k miles. A couple of weeks ago I started the car after work and it was somewhat difficult to start. Had to stay on it to get it to start. Since then I noticed loss of acceleration and power specially on the highway also my MPG is down a bit. I changed the plugs, did a valve adjustment, carbon build up cleaning, oil, oil filter, and air filter. It still has the same issue. My next step is to change the ignition coils, PVC, and knock sensor but before I throw more money at it I figured I would ask you guys what you think it might be? The car seems to be running like when you don't put premium in it. It idles fine, no light and no misfires as far as I can tell. Just figured I would ask you guys. Also I have no tunes or mods car is completely stock.