There aren't many vacuum hoses in a 300E. MB uses hard plastic line like you might have seen in a VW. You can get white line by the foot from a BMW, MB or VW dealer. Ideally you'd keep the color coding but dealers don't normally stock the various color coded lines. You can use the more common black vacuum hose in place of the plastic line but you might need a coupling here or there.

Rough idle is not uncommon in these cars and all too often it's not caused by a vacuum leak.

Sixto
93 300SD