Are you looking to mod physics or skins? If you look at mods on here that are released look and play around with the HDV files. There are readme's for Rfactor HDV files. These are essentially identical to SCE and AMS. With this you can edit aero balance, car weight, braking, acceleration etc etc. You should also be able to find engine files as well to edit - you guessed it, engine power!! These are usually .ini files. Again found in the mods folder. This will be found in your AMS directory/Gamedata/Vehicles/YOUR MOD...fish around in there.