fluttering is not 'intercooler' sound, its the sound of the air pressure formed by the turbo being pushed back against the compressor blades. yeah it sounds pretty cool, some people debate on whether this is all that bad for the turbo.
the pipe work in these cars is horrible, so shortening it would be a good idea, although the diameter wouldn't have to be bigger if you aren't going to throw extra boost at the motor.
i don't think you'll gain much and at 115kw from the factory you would want some decent gains for it to be worth buying.