Here's a video that illustrates the "Split linkage" test for Mercedes 230SL, 250SL, 280SL 113 chassis pagoda and 250Se and 280Se W108 chassis. It is a quick "rough and ready" check to see if the engine is running too rich or too lean by isolating the introduction of fuel and air. Each can be added individually and engine behaviour observed. If you add air only and the engine runs better then the engine is too rich. Conversely, if you add fuel only and the engine runs better then the engine is to