If this is just to get past the emissions testing, I'd go for it. I wouldn't leave it that way all the time, unless you want poorer fuel economy. I've had to do this for years with my old Jeep to get past the "smog nazis". I retard the timing about 4-6 degrees, lean out the idle mixture (it's carbureted...won't work with F.I. unless you can control idle mixture) and put a BB in the vacuum line going to the vacuum advance on the distributor, and readjust the idle speed. You can also create a temporary small, non visible (to the smog tech.) vacuum leak to further reduce CO and HC emissions. If your state checks for NOX emissions, this won't work very well, as the NOX will increase. Some Benzes don't have vacuum advance (like mine), just vacuum retard. Others have both advance and retard. If yours just has retard, you don't have to plug the line. So far, I haven't had to do anything to my old Benz to pass, knock on wood.