Corrected a discrepancy in file name for the Elrontur BMW M4 GT4
If you wish to apply this fix without redownloading the entire package again, go to assettocorsa/content/cars/gt4_bmw_m4_gt4/skins/Elrontur and rename 'skin_00_map' to 'skin_map'
This should now give the car the intended specular details.
Thanks to user
@Raffi_M for identifying the issue!