Mine (2008 LS 600h, 90k miles) has the same issue since I bought it last year. Since it was throwing a P0014 code, we have been trying to fix it by getting the engine timing right. P0014 has been resolved but the shudder at deceleration is still there. With my car it happens (or is most noticable) when decelerating at speeds above 40 mph. It only happens when the engine is on and doing around 1000 rpm. It only happens when the fuel pump is active (injecting gas), when fuel pump duty = 0 but engine is running, there is no shudder. I am pretty sure the issue has something to do with the L110 transmission, because GS450h models experience the same issues, and use the same transmission. During the issue, techstream doesn't show helpful data. The only thing that is noticeable is that "multi cilinder misfires" increase at a pace of 10 every second during the issue. This could be caused by the engine rpm that is affected by the shudder from the drivetrain. It doesn't seem to be "real" misfires. Transfer case fluid has been done, sparks and coils, maf sensors, crank and cam sensors. Next week it is going for service and the transmission oil will be done. I've noticed the issue in other LS600h's as well. Some more noticeable than others. In all cases the multi cylinder misfires increase during the issue. I'll let you know if transmission oil will help.