I read about the DIY sound insulating when I was researching the Z. You would need to do the trunk and the floor. Others say you really need to do the doors too and you cannot do the entire firewall unless you take apart the dash. I don't like the idea of tearing apart a new car to make it how it should have come from factory. You would also need to change the tires to quieter ones. New tires that are not shitty are probably around $1.2k? Too much time, effort and drama. The cabin noise has been a widely criticized issue that Nissan should have addressed long ago and hasn't in its third year of production.
If you're listening Nissan, you lost a sale. And, I'm sure I'm not the only one who's had to pass on the new Z for this very reason either. I was so going to get this car if it just wasn't so noisy. For shame.
