From: Retired and living in the mountains of NE PA
To make things a bit clearer, in the years when you had the option of getting either a carbureted or fuel-injected model, H-D used the "I" designation to differentiate the injected model from the carburetor-equipped one.
H-D has since dropped the "I" designation now that all Big Twin models are injected.
I don't have one, but a guy I ride with has a carbed 06. There is an old school indy shop in his home town and the owner there still works on the motor mods as long as they are carbed engines. He doesn't have the tools, skills or the desire to tune the injected bikes.