What you need to do is hold down the Break,the Gas,and the E-break and then your going to
see flames in the back tires if you didnt do it right you wont see flames.When you let go
you will get a super speed boost!!!  hope you like my cheat :)

first, you need the horn jump cheat on (x,x,x,y). second, you need to be on lisa's level
(or any other one with the dock thingy) then, get any car you like and go to the ramp near
the c-spanker ramp, turn away from the boat, and drive down towards planet hype (i think).
go at a slight angle so that most of the way down (before u hit anything) horn jump and
you should go beyond the boundry of death. it may take a few turns. when your car 'lands'
it should spin out of control and seem to breakdance. you can hold b to make lines come
out of your tyres. i recommend the cola truck and red brick car. to get out,
unfortunately, you need to restart a mission or hit start - mission select and select a
mission.

In lv.6 with Bart, go on the dock near the "high way". There is a  crate lifter. Jump on
it. And jump on the red rim of the boat. Go around the red rim and you will see a big blue
crate. Do a "double jump" and you will se a glowing orange duff card. Take it.

Get the WWII jeep. Then go where the street is streight and press on the R or A botton and
you will do a "whilie".

At the options menu, hold L+R and press X,X,X,X. If you entered the code correctly, you
will hear the sound of a horn. Then let go of L+R and hold again. Now press Y,Y,Y,Y. If
you entered the code correctly, you will hear the sound of a horn. Warning: this cheat
makes your car VERY fast, good handling is a MUST.

in the  underworld cheat it can mess up your whole game and it sucks so if you want to do
this cheat get your memory card out of ur system its happend to me

All u need to do in the first level is complete the three races and u will get a reward