Thanks for some interesting comments to me question. From what I gathered here and from some other forums, I think I can conclude that:
- the "new" 320hp engine is physically unchanged.
- max hp (320) is measured at a lower rpm than on the old 362hp motor.
- the new 6-speed trans keeps the engine at lower rpm, therefore max rpm is measured at a different rpm.
- it is easier to meet epa requirements at lower rpm
Bottom line appears that it is the same engine, bolted to a new tranny, and measured at a lower rpm.