I just finished up on the D3 1.5 install. I got the mufflers yesterday, and had them welded in today. Except for some minor tubing modifications, the mufflers went on fine.
I'm very pleased with the sound. It's quiet at idle, quiet at crusing speeds, and when you nail it, it has a clean, crisp performance note, that is just right for me!
I'm an old hotrodder, and another loud, loud exhaust was not what I wanted.
Now, if it will pull 416 at the wheels, like D3 claims, I'll be in Caddy heaven!
It's just right for me. FWIW