GUYS I HAVE FOUND IT: its the levels of the turbo that makes the flutters (for example, the level 13 turbo is a flutter and the 14 is also... I tested the 12 I think and its like a N/A car, play around with them, some have normal bovs, others have flutter)
Yep, pc version
But I had a problem I think everyone will have or already had: turbo sounds dont change instantly after installation, you have to install it at a workshop and enter your garage... I think by the time you're in it, the game does a save and updates your cars. You can just get out of the garage without touching your car (just enter and exit the garage, as simply as that) and it should update the turbo sounds.
