Changing the plugs on my '01 S430 and it's very tight to even get to the plug wire boots. You can't pull them off with just your fingers as they are too tight and you can't get a good grip. I tried this 1/2" drive socket wrench with a 17mm crowfoot socket and it works quite well. You can easily adjust the angle of the crowfoot to get at the boots in many positions and get levarage against the valve cover.