after seeing that Bojan had published a fixed bversion of some of his cars I checked out the renault and it has the same bug. Renault monaco version is the on i use. the problem is that even though the textures are 1024 x 1024 the tex file is still set to 512 x 512 so gp4 will downsample to this size thus negating the effect of large textures. all you need to do is use tex resizer to change the size of the tex from 512 x 512 to 1024 x 1024 and they will then show up in game at full resolution
note i think you need to rename .TEX to .tex as tex resizer doesnt recognise capitals