Unsolved Custom Sounds Exhaust Muffling

Hey, I was noticed that when the stock cars remove the muffler they not only get louder but they sound more raspy. Is there any way to do that with custom exhaust sounds? because when I put a muffler on with my custom exhaust sounds it still sound like a straight pipe but quieter.
Thanks

 

im not 100% sure if this is the right thing but i think you just need to make the sound louder by making your own custom exhaust sound. Just make the sound louder in the audio editor you have. I think thats what you need to do, again,not 100% sure if this is correct