The 2011 GTI is without a doubt a nice car. It performs well, is fun to drive, and the interior is first rate.
The only very disappointing aspect of the car is road noise.
I don't expect a small sporty car to be super quiet, but this car has a split personality.
I test drove it on some smooth highway and, as advertised, is very quiet.
The problem with WA State is that a lot of the highway is fairly rough, and when this car hits rough road the interior noise goes up exponentially, it even makes my old Ford Ranger seem quiet. As I said, overall a very nice car, but like most other small cars it's not going to be quiet.
Sound insulation (whether that is a dampening product to reduce noise from vibration, or a sound blocking product), will not cure the problem of road noise.
It will help with engine noise and other noises, such as those from other vehicles.
In fact, I think this model comes with a windshield that insulates against road noise.
The problem is the aspect ratio of the tires (height of the sidewall).
The aspect ratio is 45.
IMO, when the aspect ratio is less than 60, then ride comfort usually suffers and road noise increases.
I have an Acura RSX, and have done extensive sound dampening and blocking but the road noise persists on roads that are not smooth (such as rubberized asphalt).
By the way, the aspect ratio of the Acura's tires is 45 (this is the Type S model).
On some roads my Dodge pickup is quieter.
It has tires with an aspect ratio of 60.
If you want quiet, you want Lexus, but no Lexus is going to have the handling characteristics of the Acura.
No car can do everything, there are tradeoffs.