I get the dreaded code as soon as the weather warms up/spring time. during the winter I have no problem including passing inspection.Do you think it is the changed gas? And would changing my o2 sensors possibly help.

 

No it's because you probably take shorter drives and in the winter the Cat can't warm up fully so the car doesn't check it's efficiency. Once the cat warms up properly (which takes less time in the summer) the car will check cat efficiency and throw a code

 

I wish that was the case but I did many drives throughout the winter that where quite long - over an hour of driving.