I've just deactivated all my non default airports from scenery libraries, leaving only all defaults, but nothing: FSDT KJFK V2 ALWAYS THERE, SUPERIMPOSED ON DEFAULT
The problem isn't just limited to Addon Sceneries, other addons, such as UTX2 or MyTraffic2013 can add duplicate AFCAD as well.
And you should really not use caps, because it's considered shouting on a public forum.
ONLY MANUALLY DELETING THE FSDT KJFK V2 FOLDERS, IT FINALLY DISAPPEARS!
doing that just removes the FSDT KJFK, so you are only seeing 1 scenery. When you activate it, you are seeing 2.
3) MANUALLY REMOVING COUATL.EXE FROM EXE.XML THE PROBLEM IS SOLVED
Is the problem linked to couatl.exe engine?
No, the couatl.exe isn't bugged, and it's not couatl.exe that is at fault. Something on your system, (A duplicate AFCAD) is showing above the FSDT scenery.
Make sure you put FSDT KJFK on TOP of your scenery list, and if the airport scanner dosen't show anything, you will have to continually searching manually for duplicates.