I have a 99 A4 with the 2.8 and I keep getting my Check engine light
Evap purge flow low PO441 I think
First I took it out and opened it up and cleaned it, then reset it
it came back after about a month or so
then I replaced it with a new one OEM.
then it came back on after a couple of weeks
The funny thing this happins when its abit chilly outside
like Below 15'c and it does its self test then it freezes and sets
the Check engine light ????
DOes this have to be reflashed by the dealer as Ive heard a few of them
doing this even the new ones?
I can drive it like this and after 40 cycles of the key from Cold to operating
temp it will turn off the light... thats if it doesnt get to cold....

 

looks like you have a fuels system leak somewhere.
The cold probably enhances it, being cold it contracts a
hose or something witch may increase the size of a crack if it is around a connection somewhere.