Turbo sound w900

This is just a minor change to the turbo sound for CUMMINS n14 engine of Kenworth w900 SCS version by kriechbaum. I have reduced interior turbo sound for this engine only. This mod works on the updated sound mod v2.1 by kriechbaum. I am not a modder, i just did this for personal playing, others views may differ. Tested on v1.1.1.1s