A couple of years ago, several people posted the various kill/loss numbers for the various RAF, US and LW units in the ETO and it became painstakingly clear that they all killed eachother several times over, if you went by the claims.
I think the only real research have been with the BOB, which was that the LW overclaimed 3:1 and the RAF 2.5:1.
Recently on AGW, a specific air battle in the MTO was discussed, again with the LW claiming the same figher several times over (No LW was shot down)
I'm surprised to hear that the FAF claims added up; maybe the size of the conflict could have something to with it?.
I don't think that most of the WW2 pilots overclaimed on purpose. In many situations they were most likely convinced that that plane was damaged enough that it wouldnt stay in the air, but don't tell me that you have time, in the middle of a battle, to watch a plane flutter down to the ground and impact, all the way from 30.000 feet.
Daff