We operate both a 421C and Navajo and there is definitely a difference in operating costs - probably about 20%. But if you need pressurisation and want to give your passengers a good smooth quiet ride and they are prepared to pay the difference, then it is a good aeroplane. As a money maker providing you can fly at lower levels , then for pax carrying, the Navajo would beat it all the time. The engine management issue is as someone else said, simply a training issue, and I think they are great engines as they are in the Titan. With slightly higher TAS than a Navajo and the ability to cruise comfortably at mid teens, for 4-6 pax they take a lot of beating in $ per mile especially if you cannot get the 1000 hr utilization you need to operate a turbine and make money.