I have a customer that wants to purchase both of these models for a small office. Will the Konica TNP78 toner for the 4020i work in the 4000i? The 4000i uses the same IUP37 drum unit as the 5020i/4020i, so I cannot think of any reason the toner would not work or function in the 4000i even though technically it takes the TNP76 cartridge. The drum units and toners on these models have no chips to identify any differences.