Well I found what my problem at Ferrari Challenge is.
The stupid game cheats and increase difficulty based on your average ranking in the last few races...( except in arcade where the difficulty is set, which explains why I could clear arcade)
As I was working on win the US challenge with maximum points I was quitting if I wasn't about to win so all my last races were always win in the save...
I tested it by ending last on purpose on two races, and then got back to the challenge race I was working on.
Instead of always doing around 1'30'80 for the pole position the AI is now doing 1'31'60 or so........
I noticed this when on some races the best AI car was starting to be faster than me on straightline...
Well now I know what to do to fix it lol, time to loose a few races !
PS3-Xbox360 gap : 1.5 millions and going up in PS3 favor !
PS3-Wii gap : 20 millions and going down !
