It was the parameter "SpecularPow 16" in the file tex1_metall_lod0.mat
Default for planes is 4 or 5, same for objects I think, everything higher will be resulted in a burnt out picture (too much white light), so now all i need to do is extract every mat look for that string and batch replace it with specularpow 4.
I can't back up this with scientific data, but after being tinkering with materials a little in the past, I found that in IL2,
Specular value refers to how much shiny is the specular spot in a surface, so a higher value gives a brighter spot, and viceversa.
SpecularPow value refers to how big is that specular spot in the surface, so a higher value gives a much more spread over the surface specular spot and lower values a much more concentrated spot.
As the color of specular spot is close to white, when the value of SpecularPow is high enough, the white colour, covers almost all the surface, and combined with the shinyness of the Specular value is what gives this burnout look to objects (as it shows in your lower picture)
Also I believe that SpecularPow should be given only in power of two values. (so maybe better not to use 5 as value)
In short: Specular-> brightness of the specular spot
SpecularPow-> size of the specular spot (power of two values)
hope this help you to better understand.