I've been getting a couple codes on my 2014 Chevy cruze 1.4t lately. I just recently put on turbo/exhaust manifold. Intake. Valve cover. Pvc hose. Manifold catalytic converter. Now I'm getting the p0004 & p0420 codes randomly. Do I need to put a downstream o2 sensor on it now? I've run about 4 tanks off gas through it now. Any help or idea is more then helpful. I'm at my wit's end with this dang car. About to leave it running at a gas station in downtown stl and walk away from it.