You can raise your bounty as much as you want and complete that part of your milestones. First get in a pursuit and then find a ledge (ex. on top of the buses at the bus station) go as closes to the end of the buses away from the up ramp as possible without falling off and without a cop following you up the ramp. Then sit there and watch the cops go crazy. It's better if your heat is 2 or up as the lower level cops will sometimes lose sight of you and you'll cool off. At higher levels though the police will hover below you ramming into each other and everything else. This destroys their vehicles which in turn raises you bounty and length of your pursuit. You can sit there as long as you like but check behind you periodically just to make sure one of them hasn't gotten smart enough to come up the ramp.

Unlockable Cars

Car - Availability
Ashton Martin DB9 - Beat #7, Kaze
Audi A3 3.2 Quattro - Beat #15, Sonny
Audi A4 3.2 FSI Quattro - Beat #14, Taz
Audi TT 3.2 Quattro - Beat #15, Sonny
BMW M3 GTR - Beat #1, Razor
Cadillac CTS - Beat #12, Izzy
Chevrolet C6.R - Complete the game 100%
Chevrolet Cobalt SS - Available from start
Dodge Viper SRT 10 - Beat #6, Ming
Fiat Punto - Available from start
Ford GT - Beat #4, JV
Ford Mustang GT - Beat #12, Izzy
Ford GT (Castrol Syntec version) - Enter cheat code
Lamborghini Gallardo - Beat #6, Ming
Lamborghini Murcielago - Beat #4, JV
Lexus IS300 - Available from start
Lotus Elise - Beat #8, Jewels
Mazda RX-7 - Beat #9, Earl
Mazda RX-8 - Beat #12, Izzy
Mercedes-Benz CLK 500 - Beat #8, Jewels
Mercedes-Benz SL 500 - Beat #11, Big Lou
Mercedes-Benz Sl65 AMG - Complete Challenge Series #68
Mercedes-Benz SLR McLaren - Beat #3, Ronnie
Mitsubishi Eclipse - Beat #14, Taz
Mitsubishi Lancer Evolution VIII - Beat #11, Big Lou
Pontiac GTO - Beat #10, Baron
Porsche 911Carrera S - Beat #7, Kaze
Porsche 911 Turbo S - Beat #5, Webster
Porsche Carrera GT - Beat #3, Ronnie
Porsche Cayman S - Beat #10, Baron
Renault Clio V6 - Beat #13, Vic
Subaru Impreza WRX STI - Beat #9, Earl
Toyota Supra - Beat #13, Vic
Vauxhall Monaro VXR - Beat #10, Baron
Volkswagen Golf GTI - Available from start