Feature:
-CAT C15 ACERT 435-625hp and 650hp tuned engines with straight pipe sound
-Realistic turbo behavior
-Realistic intake behavior
-Custom sound attenuation for realistic sound fade off
-Custom sound orientation for realistic sound from different angles
-New Improved exhaust distortion for realistic exhaust tone
depends on throttle pressed, rpm, intake pressure and works along with sound attenuation
-Included Customizable Additional Supported Trucks (CAST) in the mod
If you don't know what CAST

Quick tutorial on how to use CAST
1. Goto def/vehicle/truck/
2. Rename one of zcustom_xx into truck def name you want
(optional but should do)
3. get inside that folder/engine/
4. Open every c15a_xxx.sii files and look at line 3
5. change "c15a_xxx.custom.engine" to "c15a_xxx.(truck def name).engine" for every files in that folder
and you should good to go

Credits:
Slav Jerry - sound modding and samples
SCS Software - engine samples
LoaderSaints - CAST idea