I have a 97 civic ex and I noticed my car starts misfiring and even my fuel gauge shows that Im using 1/2 my tank in 80 miles. I did a self-dianosis and picked up 5 codes. Code 67:Catalyst system efficiancy below threshold and Code 71-74:Cylinder misfire #1-4. So should I not blame it all on my CAT or could it be multiple things??????