I'm having a having a hard time getting the x20 boost chain for the Boosting Around the World in-game achievement in Burnout Paradise. I've tried boosting while drifting in circles. I've tried driving around the quarry. I've tried the Lone Peaks Stock Car Track. I even tried to drive around on North and South Mountain Rd. I can usually get up to x8 in all these places before stalling out. (And to be honest, it feels like the game is forcing my boost chain to stop.)
What's the best way to get this?