This is not my info. I pulled this info from comments over at Brokers Don't Care How You Win (thanks TheBigDeeb and Elodeon). I am posting this info here to help others, who are looking to complete this for the Brokers Don't Care How You Win achievement.
This quest can be completed in the Untethered Space. To complete this race easily, get yourself some [item=242371]. These need to be looted in the Untethered Space, which have been known to show up at the following locations:
/way 49.67 17.05 Untethered Xy'bucha
/way 49.65 26.65 Untethered Xy'bucha
/way 50.74 58.45 Untethered Xy'bucha
/way 53.75 45.37 Untethered Xy'bucha
/way 54.81 48.18 Untethered Xy'bucha
/way 61.33 39.11 Untethered Xy'bucha
/way 80.35 48.69 Untethered Xy'bucha
Once you have one, go back to the eco-dome and pick up the quest. Head on over to where you need to start the quest. Before you start the race, drink your Untethered Xy'bucha. Once done, start the challenging version of the race and then you can do 1 of two things:
1. Run through all the arrows to the end
2. Run straight to the end, ignoring the arrows. The end can be found here: /way #2371 74.36, 27.51
NOTE: The Untethered Xy'bucha may not be required and might be able to run just to the end without it. Give either a shot. One of them should work for you.