No roof flaps
Note: This cheat involves editing a game file so make a backup copy of the file before goimg on. Then in the game folder, open the folder with your player name. Use a text editor to edit the file "player.ini". The first number you see should be "1". Change it to "0". When you play a game and go backwards fast enough you will fly into the air and maybe do a few flips.

Cops and robbers
First go to "Opponent Manager", select a car from 101 to 140 and go to "Paint Shop". Do not forget this car's number. Now make this car into a cop car as you like, then export that paint job so you do not have to repeat this. Then, put the cars original number on its back side to identify it, for events like yellow flags and pacing times. Do this to all of the 101 through 140 cars, not the one that will be your car to drive. When your done with the cops, paint your car as you like. Then, choose that car as the one that you will drive. Start a new race. At the pacing line, you should notice that every cars are cop and you are the only one that is different. Get ahead of the pack and run, or get a few good pile ups. Indianapolis is a good selection, the straight by the finish/starting line has a narrow road for some a few pile ups. Daytona is also good as it is an easy track to drive on.

Drive off track
When your on Sears Point Raceway, go for seven turns. Now stop after the area of sand at the end of the seventh turn. You will be able to get into the space between the tire barrier and the fence here. Now drive along that place briefly until the fence ends. You should now be able to drive around on the dirt outside of the racetrack with no boundaries.