Just remember 3 things:
1. Fishtail corners if you can't slow down, so you hit the walls with your car's unpenalizable ass.
2. Wall-riding. It's usually faster than trying to slow down enough to avoid touching the walls, and can't get you a penalty easily.
3. Escort Rally car. I forget what rally you win it in, but it will clean the floor with everything, even the mighty Evo VII Rally, when tuned. Plus it's free, and thus saves you $1.35mil (That's too expensive for any rally car IMO) The Toyata RSC Rally Raid is also a good choice.
But, why is it, that to follow the CPU's driving line, you can't seem to go nearly as fast as he can without going way out to the walls?