I signed up to reply to this thread, I have a IS220d 2009. Since I've bought it, has never given me much over 28mpg locally and at best 33mpg motorway. It started giving me terrible turbo lag last few days and after reading a lot of threads I cleaned the EGR valve, which was badly coked up after only been cleaned out last year. Then I took off the rubber pipework going to the turbo. Got someone to rev the car over 2000rpm and just sprayed lot's of carb cleaner at one second intervals. Took 30 seconds to the take pipes off and I can say there is a huge difference. Car pickup is very good now, so I think the turbo get's clogged and at lower gears it is really noticeable.
Worth doing in my opinion.
