This cheat does work, i've done it before. When you start a career, choose the pergeot 206. when you get the car, give it a bit of cool paint to get you more car collection respect and also put a body kid on the car to improve the performance. You will also need to add performance parts. As you unlock more cars, go for the eclipse or impreza (these win loads of races). finally, when you've unlocked them all, get the dodge viper GTS, this car is really fast and easy to drive. Keep on adding parts and performance etc. then you will get prototype, which is even better and enter lots of curcit and show off races (these are easier to win than sprint) and win loads of respect. When you enter a show off, without crashing too much, you get a couple hundred respect from Jack, and about 20ish respect from the public caos. I've done this method, within a few days, and now i've got about 6000-7000 respect from Jack.