Traffic X has probably added another one or is it using the one from Microsoft ?
It's not using the one from Microsoft, it added a new one made for parking positions compatible only with the default, and you need to remove it.
Which one shoud I remove ?
The one in the MyTraffic folder, if that program installs its own AFCADs in its own folder (hopefully it does). In any case, the FSX Airport Scanned should help you identifying which one is the double.
Just be careful NOT to remove the FSDT AFCAD, instead.