In my opinion, the early six-cylinder engines (i.e., 2006 through 200
are optimal. Although they don't deliver the fuel mileage of the five-cylinder, neither do they suffer from failure of the plastic turbo resonator. Furthermore, the early sixes don't have the failure-prone DEF emissions controls.
EDIT: for some reason, the site keeps substituting a smiley face GIF for the "8" in 2008.