Do you have any links to the set up pages ?Get the manuals and check your linkages, or bring it to dealer. Something must not be set up right. It should go the same as my 1100C and it does 25/26 MPH both on the speedo and my Garmin GPS.
There's a few really god threads on net tractor talk also that detail how to set them all up.
I have spoken with the dealer a couple times, however they have said wait for it to run in a little. But I can't see it improving by the margin needed to perform like Kubota say.