So mechanically inclined Subaru guys, I have a 2001 H6 3.0 it's been throwing codes PO302 PO304 PO306 Misfire codes. It will hard start in really cold weather, single digits. Lots of turning over, some misses, then it fires, then slowly comes to life. In warmer weather 25° or better it will take quite a few revolutions to fire and run. Sometimes in the warmer temps it will run with no issues for a couple tanks of fuel then decide to throw a CEL. The only codes picked up are the previously mentioned. I had a Subaru guy replace plugs, valve cover gaskets, drain and refill transmission and differential fluids. Any ideas anyone?????