Sounds a lot like the vendetta sound mod.. https://www.beamng.com/resources/67-camaro-v8-sound-for-gavril-vendetta.3555/
Well i didnt use his sounds. --- Post updated --- High quality recordings using a (bolt-on)dyno, audacity for proper mixing and matching and fixing sound issues and then proper calculations of the engine code to make the physics realistic and the feeling natural. Real life driving experience is also very important to be able to relate quickly what is happening when driving and spotting inconsistencies of your calculations.
Interesting how they sound exactly the same.. I'm sure they wouldn't mind, I just believe in crediting the original creator.