Yeah, I hated the cars, too, which is why I used the gyrocopter when I found out it would work.
The only other one that's a little tough is the one where you make this tight little circle of jumps on a motorcycle. The gyrocopter can do this, but make sure you don't go too fast, it's easy to miss the checkpoints.
I saw you mention something about not being able to finish the races in Just Cause 1.
Have you attempted to do them with the Agency Helicopter?
All but one of the races can be finished with it, and it make them very easy. Well, the exception is there's one where you HAVE to use a plane because the copter isn't fast enough. You'll know it by the way it makes you fly between the smokestacks of a remote factory...
I dreaded these races, too, until I used the chopper - got my 1,000 G in no time.