So about a month ago I had my car throw a p0174 and p0171 bank 1 & 2 system too lean code. My mil light went on for about an hour and in that time I had it checked to reveal the codes and then it went off and then about a week later the light came back on and then again after about an hour of driving it went back off. And my car is getting very shitty mpg and also when I'm cruising and I floor it to pass or just floor it in general I get this horrible rotten egg smell. It is very mind boggling because there is no check engine lights on and it's still getting horrible fuel mileage. Like 12-15 mpg Highway. Iv cleaned the egr port so far but that's it. Anyone have any ideas or the same experience?

 

rotten egg smell = bad catalytic converter.