190e 2.3-16V fuel economy

[190Blacksmoke]

Ok here is the deal. I am sick of this. My 190e 2.3-16V is wasting a TONNE of gas! I am getting 230miles to a tank. Thats about 14 miles a gallon! And that is all highway driving. I am in the city for maybe a few stop lights if I hit them and then its all highway driving. This seems to me a little odd as this car is apparently supposed to get 29.5 miles to a gallon on the highway. I have put a new fuel filter in, the plugs and wires have been changed, fuel injectors seem fine. Completely new custom exhaust installed 2 weeks ago. The o2 sensor light comes on then goes off but I highly doubt that it would cause me to cut my gas mileage in half. Also worth noting is that this car has barely any power in the low gears, and yes the camshafts are fine and the timing chain is installed properly. Just wondering if maybe the ignition timing and o2 sensor together could be causing this great loss in power and fuel economy. I am looking for any help here! Thanks a tonne for looking at this!