Be very careful if you run this as written. Know your party, which might defeat the point of being an AL adventure.
The problem I ran into with this adventure is actually at the very start. My players never even got to the race. A couple of them got too distracted playing Sherlock Holmes and then they got side-tracked by other things going on in the city.
The adventure is all about creating a cool fun shiny thing, Na N'buso's Haka, multi-event race. But then it drops this evil plot hook onto the race which is effectively like jingling keys off to the side. Depending on how easily distracted your players are they may get sucked into investigating that rather than doing the event.
The hook to the adventure is tenuous as to why they would do a race rather than go around asking questions and searching for clues. To fix this issue I would completely remove any hints about some kind of plot if your players already want to do the races, which they probably do. If you still want to hint/foreshadow, do so very sparingly. Instead build up hooks around why your players might get a special chance to compete in this event, ideally related to things they've done already. Or make a mini adventure to win entry.
At the end you can have the evil plot unfold as written and the investigation can start.
On top of all that it's pretty lame that the entire plot hook for why the players should be in the race to investigate is that the cheating might be happening during the race. Then, in the end, that's not even true and what my players ended up doing actually made the most sense. Ironically, they staked out the pens instead of joining the race.
Also, as others have said some things feel kind of racist.
[1 of 5 Stars!]