Stock redline should be around 6750 or so, peak torque is at 4000 and peak HP at 6000. You can look up stock dyno graphs on various websites to see for your self, but like stated above nothing wrong with shifting at peak torque (4000) unless you love to burn gas and or are racing and need the extended rpm.
When the duratec was a new engine in the focus and we were all trying to figure things out, most agreed that 6k rpm was a good place to shift with a 2.3. That is about when hp starts to drop off significantly. I usually shifted by 6,400 while racing in 1st, and around 6000 every other gear. With a tune I could rev it as high as 7,400. I would think the shift point would be similar for a 2.0. Look up a dyno chart and decide for yourself.
I was just looking at 2.0 dyno charts though and they seem to keep good power while revving it to the sky. You may just take it to almost the fuel cut out.