I have a 2003 Passat Wagon W8. It just turned over 104 thousand miles. However... about two weeks ago the enginge light came on. After a little bit of research and a diagnostic from Auto Zone I was told it was an Emissions System Control Leak. i asked a friend who owns a Audi and loves both that and Volkswagon... he did a little research and after that came over and reset my computer and told me if it came back on to tell him right away. Well that was about a week ago.. and this morning it came back on... I am very concerned as to what this could be.. and Im not sure even where to start looking for solutions. I still have much learning to do about Volkswagons.
If anyone has any insight what-so-ever on what could be the problem I'm willing to test and theory. i'm hoping for speedy feedback.

Thanks for the help in advance.

Sam

Edit/update: Also in accordance to the engine light coming back on... I started my car yesterday with 85 miles (according to the dashboard) and have only traveled about 60 miles and have had to gas it up again. it went down so fast it amazed me. from 85 to 25 miles left when I parked it this morning... and then I went to start it and leave for work this evening... it said 5 miles left. My friend thinks its a O-2 Sensor)

 

The check light sounds like the O2 sensor, but as for the fuel gauge... that is something totally different.