Any ideas on how to fix the family wagon..

We have 99 passat wagon we bought used 5 months ago. Has only had one owner
and been well taken care of has 135000 miles. It stated a couple months ago that it
would surge while driving every once in a while. It stared getting worse where the rpms
would surge while idling and run rough, would smell like exhaust, when you give it gas
it would struggle to move then suddenly go and sometimes would die. It was only
happening once in a while and when you recycle the motor it would stop. Well
yesterday it surged very hard while i was driving and the C.E.L. came on. While idling it
was running very rough. I turned to get on the free way and it would not go over a few
miles an hour when you gave it gas. Tried recycling it but it made no differance then the
car died. It would start no prob but would idle rough then die. We towed it home just
replaced the fuel filter but it is still doing it. If anyone has any ideas that would be great.
One more thing it only seems to do it when the motor is warm.