The thing about my Mod. It only has 2 volume adjustments in it when you boil it down. Lowered transmission noise and the UCP raised tire squeal. All other volumes are stock game levels. I think what this has done is made Engine noise more prevalent(which is what I desired).
An interim fix for you until it's decided on actual sound levels for the UCP(or if they will in fact be included or left as a stand alone mod) would be a quick edit of the ..\MODS\Trans NVR Mod\Audio\carsoundconfig.xml
file that is included in my little Mod package.
For louder tire squeal edit this line in the file above(a whole number in data=
is a 100% increase in the sound files recorded level)
<prop name="SurfacesVolumeOverride" data="2.0" />
Conversely you can lower all the cars at once by lowering the engine volume in that same file or this line as it were:
<prop name="EngineVolumeOverride" data="1" />
Reduce the data=
line. Again a whole number = 100%, 0 would be off, 0.01 = 1%
I had played with the idea of creating a Visual Studio app that would read and write the carsoundconfig.xml and give the user a GUI interface outside the game with sliders to adjust the various Override Volume and Reverb levels, as well as the 2 different 3D Pan levels.