Ok this all started a few weeks back i was driving home from work and i noticed my fuel gauge had gone from half full to full and the DIS said i was going to get a total of near on 900 miles out of the tank. I drove the rest of the way home fairly heavy footed and when i got home it was back down to just under half. Since then my current MPG on the DIS is very sensitive as soon as i lift of the throttle it says --- which is confusing. i can still get 360 miles to a tank if i drive fairly steady. Lastly at the MOT i was told it was very difficult to pass the emissions although i didnt get a read out for some reason.
Any body had anything like this and any idea what it could be?