Maybe we're miscommunicating here.

3,0 has one muffler (going sideways), and the tail pipes are pretty long (and skinny compared to the opening in the bumper). With the oval tips fitted to the 3,0 there is some room around the tips (same as on the V8!), and you can see some thermal wrapping if you look at the tips at the eye level (very nicely photographed above). If you look at the V8 tips (at the eye level), they have the same space around them as they come through the bumper. Maybe the V8 thermal wrap is laid out differently, but the opening in the bumper is the same, and there are no inserts to go around the oval tips.

I don't know how to explain it better, but there are no inserts, that can close the gap between the oval tips and the bumper.