The reason the booster isn’t working is that the car is clipping the edge of the track I think. I noticed the car spawning incorrectly, I need to adjust the timer to fix that, it normally happens when the game lags for a moment.
Also here are all the booster tricks I discovered
The first one is real, I only got it once and haven’t been able to reproduce it. (Not sure if the second and third booster can be chained together like the image shows)