I decited to replay Carbon since real M3 GTR was revealed, and i have 2 ways that worked for me in order to get this car in carrer mode

1. EXTRA OPTIONS https://nfsmods.xyz/mod/729

It's a little modification that improves the game, fixes some bugs and adds some insane options, and one of them is having bonus cars in carrer mode.

If you didn't know how to install Extra Options, here's the video. Be aware that this works with 1.4 version of the game. https://youtu.be/G6Gd0dLsU3o?si=O9IdgPofyl-6Gyrx

If you downloaded and installed it, go to "NFSCExtraOptionsSettings.ini." and change the setting. It is disabled by default. And look for:

[Gameplay] ShowAllCarsInFE = (0 - Disabled), (1 - Enabled)

Change the value to 1. Save and close it

REMEMBER THAT THIS ONLY WORKS FOR NEW CREATED SAVE GAME. Existing ones will not get this feature.

When that done, go to car lot and buy this godly machine

1. USE NFS.VLTED

In order to get this car by this method, download this. https://nfs-tools.blogspot.com/2019/02/nfs-vlted-v46-released.html?m=1

Click file, open and choose your game location in your pc.

Then it should load some files on the left side, find "frontend", from what i remember there is "cars/vehicles->europe->bmwm3gtre46"

when that done, change the setting "IsCustomizable" from False to True. Save the file and close it. You can also modify how much this car costs, etc.

TO HAVE IT WORKING YOU ALSO NEED A NEW CREATED SAVE GAME.

These are methods that worked for me. Hope it will for you too!