I just got all the achievements for Midnight Club : Los Angeles. The two achievements above were the hardest to get. The requirement to get the first achievement is to invite 5 friends to a game lobby. I had hard time getting this achievement because I didn't know 5 people that were playing this game. Some time later I met some people and they helped me get it. The second achievement was to collect all Rockstar barrels, and some of barrels were very difficult to find.