Car mods in Online. Is it even possible now? And how if possible?

[Frozedon]

Hello guys! i've seen lots of screenshots with car mods in GTA:O... Today i wanted to try this (yes I love to risk and get banned lul) but GTA said "Your files are edited so go f*&ck yourself"
Is it even possible to play online w/ car mods?

P.S.: Sorry for my english skills and for asking about Online...