i didn't weigh it but the carbon is considerable lighter when i compared the pieces.
If you ever get the chance, I would love to know what your bike weighs with a full tank on a calibrated scale. Materials recycling places have them and barring that, you can get two bathroom scales under each tire.
I would bet your bike weighs around 410 with a full tank. I'd love to also know how much the carbon tank you have coming weighs against the OEM tank.