Back in the days, I loved GRID, but couldn't compete at difficulties higher than average. Then I got good, and started to consistently nail the AI. Still, when AI drivers got out of corner with me, they accelerated much quicker, unfairly gaining speed and position in front of me. Sounds familiar? Still, I owned them, and wanted some challenge.
This was the time when I found the Life Career mod, which was pretty good at changing the game in so many places, but did one thing wrong. It made the AI even more unfair. At some point I saw a 350Z moving away from my NSX like I was standing still. I wanted to change this, and stumbled upon some wonderful modding tools from Ryder25. Check out his website, it's at Ryder25.com
After playing with tools around I quickly noticed the catch-up values in the original game. Turns out AI couldn't compete with you fairly, so it received up to 2 times more power while behind you and overall had more power even close to you. The whole pack of cars remained closely rubber-banded to you from start to finish, no matter what you did.
This was the first thing I removed after figuring out the modding process. Still, the AI needed some way to win, so I continued figuring out how to optimise their driving.