Havent heard of engines needing a decoke these days as modern fuels are pretty clean. It may have been doing too many short runs and the PDF was clogged. But as the turbo has now gone it may have been degraded oil possibly due to known camshaft problem as they dont seem keen to tell people about that , assuming your car is in the range.
Anyway welcome to the site and I am sure you will enjoy your cx5 as they are a nice car to drive.