My 1996 VW Jetta GL 2.0 idles rough, puffs n putts when I first start it in the Morning. And if I let it sit long enough to cool down significantly after driving, it does it also. Once the car is warmed up and in use throughout the day it seems to start and idle fine. My fuel mileage is down around 15 Mpg. I smell an odd smell once in a while when i park my car after driving too. I am reading a few Oxygen Sensor codes too, coming from Bank 1 (the Upstream Sensor). Could this be a significant contributing factor? Any Ideas as to What could be my issue? THANKS !!