I bought a used 05 cobalt 2.0 sc around 3 months ago, from the beginning I've constantly been replacing parts to get the car up to par. My current battle is agents normal operating temp range misfires and slight engine vibration. You can hear the miss from the exhaust and I've about fully extended my wallet. The cars bone stock except for a typhoon cold air intake. Parts I've replaced would be maf, upstream o2, camshaft position, cleaned throttle body, new head gasket and intake, new timing chain, fuel filter, new plugs gap .32 nkg, new air filter, cleaned grounds, new battery, I've about given the car the whole once over. The only thing I've been able to do that seemed to even it out was to disconnect the pcv hose from the valve cover which connects to the cai and suck air from it. In my opinion I find that quite odd but I'm in uncharted territory for my knowledge. Any help would be greatly appreciated, I also have a snap on diagnostic scanner so I can provide sensor data, I'm just unable to Interpet it.