This time I just made a pack with several sound options for the Nissan Skyline in order to replace vanilla V6-ish sound, choose which one you want and enjoy the sound.

Changelog:
V2.2
-2F2F: Renamed to Prostreet, tweaked RPM values, changed sound files order and fixed sound conflicts with Nissan GT-R R35
-Straiht Pipe: Renamed to Undercover, tweaked RPM values and fixed sound conflicts with Nissan GT-R R35
-New sound options: GRID R32, GRID R34 and NFS Unbound

Installation:
Open one of two folders with sound you like, then drag and drop VEHICLES folder inside it to your game directory, make sure that you made a backup of original VEH_2076524_HI.BNDL file

Sound Demonstrations: 
ProStreet: https://youtu.be/73fG3-3W7AE?si=M-3u58wSLvkEcvUU
Undercover: https://youtu.be/XqswUErjiek?si=UMrdm26NAadqvurs
Unbound: https://youtu.be/D3aKjFeitI8
GRID: https://youtu.be/7AoFQBeb9yQ
GRID v2: https://youtu.be/JN1MSF0vE3o

Credits:

DGlorio: for MW12 Exporter/Importer
7ndrew: for tutorial on how to extract .gin files from MW12 as well as Raimo i just reversed process
The_Unpunished: for Gintool
BaiAlbert: for finding out how to fix the fin files conflict and adjust the RPM
X6zmeisteR: For GRID Legends sound dump