I think you are one chain link off on your pump sprocket. I think that is 18 degrees but not positive. Possibly occured when some past owner changed the chain out. Hopefully he did not pay a garage for a quality job. The good thing is it should seem like a different car when you get it to 24 degrees btdc. Out of curiosity what are your idle issues? I have two 240ds as well. That car had to be slow. Not sure if you can work enough slack into the system to move a tooth. Others will know as that error is not uncommon.