I got a little cheat that will guarantee that u always come #1 in the arcade and tournaments (only works in total racing, and non-knock out races). All you have to do is look for a place with weapons and camp there. Then fire weapons at cars that come by. Worried that if the other opponents finish u dont get points, well that is not so. The opponents will keep on coming by u until u finish the race, so keep on collecting weapons and firing. The opponents no longer shoot each other once they finish their race so they dont get extra points. I find that a total of 30000 is usually sufficient. then just finish the race.
I find this good with tracks that are impossible to race on.