How to set up a equal length header? 2 different sounds for one vehicle

I'm working on a engine, and I want to add a equal length header to it. How would I go about doing this?

 

"2 different sounds for one vehicle"

I know that you can have a separate sound for the engine & exhaust, but having 2 separate engines sounds? Not sure about that. There might be a way to do it, but it would possibly require some coding

 

Hmmm... I'll keep trying I guess. Until then, no equal length for my EJ207