Hello, I have a 2000.3.8L Impala that has the check engine light on with codes P0171 bank 1 cylinder 1 and code P0302 cylinder 2. A little info that may aid the people or person to be able to find the proabale scenario with my car. It has no catlaytic convertor and a pipe welded in its place. It was a used vehicle lol not my choice. It has subtle vibration/mubling while in idle. It has no white smoke and overheating at all. Hope you all can help. I thought of just a tune up with spark plugs and distributor cap along with replacing the cat but I wasn't sure if it would fix the problem. Also the intake manfold was repairded due to the cat giving out maybe some vacumn leaks as well?