Guys, I'm getting check engine codes 174 and 171 on my 96 with 5.8. I've cleaned MAF sensor twice, new O2 sensors, new air filter. Visually I don't see any vacuum leaks but haven't done a smoke check yet. My Innova scanner has the "CAT" icon lit up in red.....could I have a bad catalytic convertor that's causing my problem? Vehicle drives fine.