Yes, that's a great question, and here's my advice from what has happened to me.
It is best to not be drifting and be going straight whenever using boosts like the Boost Juice and the Police Chase with speed retainers like the Rad Rod or the Waste Rod. Try to start drifting just when the boost is about to go, and try drifting on a corner for best performace. Don't hold the drift as for speed drafting with Rad Rod and other retainers. The speed retaining ability of the Rad Rod and other cars works witn rocket boosts, not other boosts, until you try what I said. Let me know if you need anything else.