There are some other great sound mods out there, but the consistency of both quality and pace with which you are getting yours out is really impressive. This I believe Toyota sourced engine sounds like a cammed, small displacement DOHC engine with a supercharger should.
I know I have been pushing it with the suggestions, but if there is any chance you could give some of your time to this flat 12 glory, that would be beyond awesome (I hope you guys enjoy this vid):
https://www.youtube.com/watch?v=KHgD0wJGcR0