Have you tried it on single player missions? Some multiplayer servers are running with lower graphic settings, that might be the cause.
I don't see how a server would be able to enforce any graphics options settings other than civilian traffic and scenes so I doubt that that would be an issue. However, ambient lighting plays a big role in how the TGP views things. White hot may work better at dusk and dawn but become much too bright at high noon with no clouds. I have found that 512 resolution works best and always try each TGP mode for each mission to see what is best for that particular mission.