Forgive me for saying this...
but unless you cut open your muffler to see if you actually got it clean... I believe you are stating as fact an assumption on your part.

We do not know what, if anything ,was IN your muffler to start with either ....

http://www.teamec.be/cms_files/Flushing%20and%20Cleaning(EN).pdf

''High side muffler assemblies''
This is used on some car applications in order to reduce the so
called pumping noise from a compressor. The design of this part
makes it impossible to flush it, clean and remove all the debris.
Older muffler designs even includes internal small parts that held
even more debris when a compressor failed. If you think on a
restriction of this part, don’t take any risk and replace it by new ''

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html