Board Thread:Game Discussion/@comment-76.26.3.77-20150505032049/@comment-25956839-20151114135513

Yes, if you upgrade the car, when you buy it later, the upgrades will still be there, normally the in game description is along the lines of..

"If you start to play the event, all upgrades, customizations and VIP will remain on the car permanently, whether you acquire it from this event or buy it later."

- In-game quote.