Hi and welcome to LOC
Since you ask are you aware of the head gasket issue?
In a nutshell basically Lexus have admitted to a design fault with the HG on the 220d. It fails! Lexus have an extended goodwill warranty of 111,000 miles or 7 years old if the car has a full lexus service history. If you car falls into that bracket and the HG fails they'll replace your engine for free.
Also check any re call issues have been cleared up such as rattling dashboards, shaky rear view mirrors, faulty fifth fuel injector.
Also keep the DPF nice and clean. This car will perform better if used for long journeys. doesnt like short trips and this tends to lead to it clogging up. And also some have had EGR valve problems I believe.
Do a search on IS220d head gasket on this forum and you'll see what I'm talking about. Also the other probs I've mentioned are documented extensively on here.