This mod is Cummins ISX12/15 and X15 engines with straight pipe sound
This sound will be replace Cummins engine sounds in SCS trucks and selectable engines in modded trucks
(If the mod doesn't work on any truck you can tell me to make this mod support other modded trucks)

Feature:
-Cummins ISX12, ISX15, X15 370-650hp engines with straight pipe sound 
-Dynamic sound focus for more rumble exhaust sound
-Custom soun attenuation for better and realistic sound fade off

Version 4.0 Changelog:
-Renamed cm870 and cm2250 to ISX and ISX15 and will be stock EGR and VGT version
-EGR and VGT deleted version will be ISX with N14 turbo and ISX15 with Holset HX60W Turbo
-VGT Deleted ISX use jake brake, and the rest use interbrake 
(Note: Because 3rd stage interbrake is done by VGT mechanism, so VGT Deleted ISX15 won't have difference between 2nd and 3rd stage)
-Removed X15 engine as it gonna be its own mod
-Whole new engine specifications
-Reworked sounds of course

Version 3.0 Changelog:
-Rebuilt the ENTIRE mod
-Separated engines and sounds into 4 variants:
ISX CM870 400, 450, 500, 525, 550, 565, 600
ISx EGR 400, 450, 500, 525, 550, 565, 600
ISX CM2250 450, 500, 550, 600
X15 400, 450, 500, 525, 565, 605
-Included idle jake brake system
-Included Improved Customizable Additional Supported Trucks (CAST) in the mod
If you don't know what CAST is :

Quick tutorial on how to use CAST
1. Goto def/vehicle/truck/
2. Rename one of zcustom_xx into truck def name you want
and you should good to go

How to use idle jake brake:
1. Hold light horn button for 1 second and release (release in 1.5 seconds) 
2. tap light horn button once again, and idle jake brake should be engaged
3. Repeat the same process to turn off 

Note: idle jake brake system will not work with some kind of interior sound mods

Version 2.0 Changelog:
-Updated for 1.42/1.43
-Rebuilded sound 
-That's all (actually)

Version 1.5 Changelog:
-New exhaust sound sample
-New custom sound volume angle for extra realistic sound angle
-little more improvements

Version 1.4 Changelog:
-Supported SCS International LT

Version 1.3 Changelog:
-Supported all RTA trucks (except some old trucks like pete359)

Version 1.2 Changelog:
-Little improvement on exhaust sound
-New jake brake and blow off sound
-Sound will be replace on GTM Kenworth T800 Cummins engines

Version 1.1 Changelog:
-Fixed International Lonestar engine error
-that's all

Version 1.0:
-Initial Released

Credits:
Slav Jerry - sound modding
SCS SOftware - main sound samples