Will an ECU from a 2000 A4 1.8tQ work in a 2001 A4 1.8tQ since they're both DBW, or not?

 

no, the numbers on the ecu have to match..

dbw doesn't have anything to do with it

 

Its not the numbers on the ECU, its the letter that matters. Its the last digit/letter in your ECU "number." My ecu number is "4B0 906 018 Q" also refered to as a "Q box". So if i needed a new ecu all id have to worry about is getting one that part # ends in "Q"