Hi Steve,
I agree with Chris that the symptoms can be a little subtle initially with the issues related to the head gasket on the Lexus 220 diesels. If you have not seen what Chris has described, I am sure that you will see the pink engine coolant sprayed around the engine bay. The coolant is pushed put due to leaking gases which can be tested. The IS 220d are prone to head gasket failure, and I think in your case the white smoke could due to low cylinder compression arising from to leaking valves, piston ring sticking, or o-ring wear. I am certain that your egr valve is also fully corked up too! Thre are lots of other members reporting similar issues under egr, dpf, and head gasket etc. I suggest you get your car to Lexus, and provided you have some service history, you could get get this repaired under their extended warranty which is 7 year/ 110 k or so miles. I had mine done last year, new engine (most of it), now feels like a new car even if it is 7yrs old!! Let us know how you get on.