I had a problem with the rotten egg smell and the cabin filling up with exhaust on my 2009 IS 350.The rotten egg smell was from my faulty o2 sensors needing to be replaced. 60000 miles is not a bad time to replace them ,but what do I know?As far as the cabin being full of exhaust everytime I rolled the window down, this is because there are two vents located in the trunk to allow air in to cool the amp and ventilate the trunk.Some how the vents stopped closing and started allowing exhaust fumes in since they are almost right next to both tailpipes.The exhaust ends up in the cabin from the suction caused by opening a window while driving .Plug these vents and there will be no more exhaust fumes inside the car.Took a year and a half to figure this out.Someone online mentioned it.Thanks who ever you are.
