For this, you'll need the "NFSW Fuck The World" Trainer by [Only registered and activated users can see links. Click Here To Register...]. You can find this trainer in the forum.
1) Start the Game and set resolution to 800x600 and Windowed mode.
2) Go to your garage and select the car with most expensive parts installed in it. (Better if it's an T3 with Ultra parts.)
3) Run the Trainer.
4) First press "Ctrl+F1" to activate the anti-cheat bypass.
5) "Ctrl+F4" to activate the car hack. (Sesto Elemento).
6) Go to Free Roam and then back to the Safe House.
7) You'll see that your car has changed to Sesto Elemento.
8) Go to the Performance Shop.
9) You'll see that this car has all the parts that were applied on your original car. Sell those ultra parts by dragging them to the selling section on bottom right part of the screen. (Don't worry, you won't lose the parts.)
10) Save and go back.
11) Repeat this several times. (I got $150,000+ per one time and I continued this for 10 times. When the error message comes as there was an server error, just click OK and continue.)
12) Turn off the Car hack and go to Free Roam. (Still if the car hasn't changed, go back to the safehouse and then back to free roam.)
13) Go on any race, pursuit you want and win/complete the race.
14) At the end of the race when you recieve cash for the event, you'll receive the cash you've collected by the trick too. For me it was over 1,000,000 :) )
Enjoy. Press THANKS if you liked it.