[Klemm]

How does the game know to look into MODS\My3do\plane\Texture to find this effect??? :?

C'mon, you should know how the current wrapper works. Judging from your post count, you don't seem to be new around here.
The modded il2fb.exe looks for the wrapper, which looks for a directory called "MODS". In there are many folders (depending on how much mods you have of course), and in those folders the file structure of the .sfs files of the game is recreated.
So the wrapper looks at the folders, takes whatever files are in there to load them before the original game files. And when it is done, it loads the rest of the original game files.
It loads the modded files in alphabetical order, so having duplicate files in the MODS folder can lead to conflicts, but much more likely to omissions.

Or did you mean that this path doesn't exist in the original .sfs files (as stuka_40 has now posted the correct path)?