just thinking out of the box, I believe F360 boxes are starting to come into the 'affordable' bracket (just had a look on ebay, none there today
). Most builders who have used them comment on their pleasing note, even if not from a flat plane v8. But, I've not heard of any running from the Toyota 4pot. JD had his running from his Peugeot v6 as did another extreme builder.
This would not be a simple install and would be an expensive test, I've spent in the region of £800 on various bits and pieces to try and get close to the raspy Ferrari sound, I think that's enough for now
Might be an idea to ask some builders/owners for sound bites to hear their exhausts and then choose the best suited to you
Darren