I did the borrow glitch once. (basically, borrow a car, delete game data (the game install/updates), go into game and change cars (do NOTHING else), reinstall updates) There are problems, some of which can be avoided. Pictures, replays, and created tracks get deleted, so they need to be exported first (I forgot) The unavoidable problems, to my knowledge, are that some garage thumbnails get deleted, and it takes time. I also made the mistake of accepting a gift car and getting in it or viewing it in my garage. It wasn't a special car, but something about it (perhaps the gold chrome paint) made it invalid to the game (before restoring updates) when I viewed it. So now, one of my games has a car in it that is unusable. I can't get in it, sell it, tune it....nothing.
I wouldn't recommend it, especially with the easy money that's available these days. The only 2 cars I can't get yet are the normal X2010 and the Prototype don't think I'm hurting because of that.
About the X2010 Time Trial...with a gold time of 1'25, it's actually quite a bit easier than the special event Vettel Challenge, where Suzuka requires 2 laps around 2'20, or ~1'10 each. I managed a 1'07 in the Seasonal and 2'14 in the Special Event - Red Bull Vettel Challenge, still 3 second off the silver time.
