Instructions
Visit any of the Internet cafes in Liberty City, and check your email for a message from Brucie. He will instruct you what type of car you need to steal, and where in the city the car is located. You will receive a new message from Brucie after you successfully steal and drop off each new car.
Defeat the guys guarding each vehicle you attempt to steal. Most of the vehicles Brucie asks you to steal will be guarded by several armed men you must defeat. A gunfight will draw the attention of the police, who you must then lose before dropping off the car at Brucie's garage.
Head to Savannah Avenue, east of Meadows Park, when ready to steal the 10th and final car. Quickly hot-wire the PMP 600 before the car's alarm brings the police to your location. Drive away and lose the police cars prior to returning the car to Brucie's garage.
Drop off the car at Brucie's garage. You will now have the option of adding the previously unavailable PMP 600 to your fleet of cars. Drive the car from Brucie's garage to your personal garage, to add the car to your fleet.