Next time don't install mods which modify your handling files or give you any kind of advantage over another player. They are not allowed.
Advantage over players? Hah, well the only advantage he would have over the players is having a better looking car than them in his screen.
Anyway, VC-MP has this sort of "anti-cheat" programmed into it which restricts the editing of the following core game-files: data/default.ide, data/handling.cfg, data/weapon.dat, data/VCMP.SCM and data/pedstats.dat. I don't know if any more have been added over the years but I wouldn't want to care either.
Next time you install a modification, make sure it changes nothing but texture and collision files since any major changes would be considered as an attempt to cheat by VC-MP. The default.ide/handling.cfg can be googled. I'm not sure if I'm allowed to post my own links to files like these here so I won't risk it.