It is my understanding that every time your ECU is flashed, your ECU's 'flash counter' is incremented by one and this count cannot be reset (even if you flash back to stock). In fact, re-flashing to stock would show that your ECU was flashed twice.
Unfortunately this will not tell you what kind of flash you have, just that something was modified at one time. I don't believe VCDS shows the flash count, and even if it did, it wouldn't tell you much.
Supposedly Audi dealers have the ability to check the flash count. That might tell you if your car is (and has always been) stock but not much else.
According to an Audi letter found here:
https://www.audizine.com/forum/show.../showthread.php/498282-TD1-info-from-Audi-TSB-You-ve-probably-already-seen-this
"Audi's current dealership level diagnostic equipment allows for automatic detection of unauthorized ECM tuning on many current vehicle models. Every new model year will bring more vehicles which will automatically be detected;
this detection runs automatically in the background of the normal diagnostic process, and will be completely transparent to the technician working on the vehicle.
If an unauthorized ECM calibration is detected, a "TD1" code will automatically be populated within the Warranty Key section of ELSA web. Not every tuned vehicle will be detected automatically; however, selected vehicles can be checked for unauthorized ECM software by performing a Specified vs. Actual ECM Software comparison. This warranty code cannot be manually added or removed."
A better test would be to have your car 'dyno'ed' to compare expected output to its actual performance. That way you not only know if your car was tuned, but the 'quality' of that tune.
