I've been trying to get to the bottom of my air leak problem and I noticed this fuel line that appears to be wet - there is greasy black stuff on the line. I'm not completely sure, but I think it is the return line. A leaky return line doesn't hurt much on the diesel side since it returns to the tank, but on the WVO side the return is looped, so if it is leaking air it could be contributing to my air leak. Check out the pics below - do these lines look like they need replacing?

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Autos:
1991 350SD 276,000 miles
2001 VW Beetle TDI 115,000 miles

Horns:
1955 Selmer Mark VI Alto (55,xxx)
1958 Selmer Mark VI Tenor (85,xxx)
1964 Selmer Mark VI Tenor (125,xxx)
1967 King Super-20 Tenor (430,xxx)
2002 Selmer Series III Soprano

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it cant hurt, 25 year old rubber is bound to break down at some point!

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82' 300SD

Yes.

Not contributing to your air leak though. This line would only be open on the diesel or purge settings. On the WVO only the entire diesel circuit closed via the solenoids.

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1982 300TD 210K miles ("The Replacement" aka "The Anvil") - SOLD
1979 300SD 245K miles (never ending project)
2007 Pinarello F3:13
1995 Ducati 916 (SOLD, sniff)
1999 Ducati 900SSie (SOLD)