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For this you need a very fast sports car (e.g. De'Leo Stiletto, Samson Duke, Samson Opus).

The route you'll want to take goes from south-west Frisco Fields over the bridge to Barclay Mills, through the tunnel and down the hill. Just follow the main road after passing the bridge. Because you will be driving downhill you can easily keep your speed.
Later in the game you can also unlock upgrades that improve the speed of your vehicle. So if you have any trouble wait until later.

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