Wow...no replies....anyway the exhaust noise is all about the back boxes...just rework them either with new ones or core the existing ones.
The only other way is to decat the car but thats silly money.
Its up to your budget....Maptun etc all make systems for the 2.8....only xwd owners are limited for choice.
i removed both cats and the resonator in the centre and the sound now is unbelievable, totally standard albeit a little louder when driving normally,
open it up though and it sounds like a full on race exhaust, i,m still amazed how easy it is to drive quietly and then in seconds it can be transfomed into something that sounds like it should be on a track