I won't waste my breath, or fingers, going into detail about the specific cheats. If you don't see them, lucky for you.
Seriously though, the AI is horribly contrived, and I don't just mean in an unfair way, because equally significant to the problem is that if you're lagging behind, they slow right down to let you catch up.
For example, I was racing single-seaters at Spa, but because the game doesn't appear to have a time-trial mode (the demo did, where did it go in the full version?), and because I wanted to have a bit of free space in the track to practise in those cars, towards the end of lap 1, I slowed down and let the AI drive off, giving them about 30 seconds advantage. I start lap 2 at full speed and to my dismay, by the time I came round turn 1 hairpin, I could see the AI down in the dipped chicane thing slowly creeping along. I caught them by the start of that long straight just after that dip, and lo and behold, as I raced past them along that straight, some of them starting surging past me again. Where did they find this incredible pace from? There's no slip-streaming in the game. The cars are all of equal power and speed. And why had they all slowed down so much in the first place?
I'm afraid when I see this sort of thing happening, the alarms bells ring loud and in my eyes, the AI loses all credibilty. It's not real AI, it's a contrived solution to generate "excitement".
Incidently, Codemaster have openly admitted that they used this sort of "catch-up" AI in their past games. They admitted it when being pestered, by people like me, about their AI at at time when they were insisting that they had dropped this technique for the Race Driver series, which they wanted to be more sim-like. It's clear they have brought it back, and at the same time have reverted to a far more arcade approach overall. To be honest, they probably get fed up being moaned at for their poor attempts at sim and decided "screw those sim gits, lets do what we want this time."