Just perfomed diesel purge (plastic bottle method) on my '83 300D last week. Valve job was done two weeks previous. Did not notice any noticeable performance improvement, nor did she produce any abnormal smoke from tailpipe. It did however turn the bronze colored liquid black when it was returned to the bottle. Not sure if that is normal, but after changing both fuel filters, she seems to be running as she previously did. By the way, the bolt on top of the primary fuel filter was a 24mm.