If you go into world editor (f11) there will be something called "window". If you press it, there should be an "audio" option. Hovering over that will give you an "engine audio" debug or editor option. If you decrease the main gain, you can decrease the overall volume of the engine.
I don't know if anyone has ever seen this or has been mentioned before, but... The temperature needle on the Evo IX is misplaced.
Ill look at fixing it if i get the time --- Post updated --- easier than expected ill update it in about 20 mins --- Post updated --- Needle update is up https://www.beamng.com/threads/mitsubishi-evo-ix-fix-on-page-20.73123/page-20#post-1450085
Tried this? https://www.beamng.com/threads/mitsubishi-evo-ix-fix-on-page-20.73123/page-20#post-1450085
https://www.beamng.com/threads/mitsubishi-evo-ix-fix-on-page-20.73123/page-20#post-145008 Edit: make sure to clear cache if you have used the original version