I'm sure I'll be in the minority here, but if the EGR is disabled (as it should be on these engines), what's the harm in letting the engine consume it's own oil vapor? It'll never build up in the intake manifold or create the tar-like deposits that the EGR soot creates. The oil vapor deposits in the intake manifold cause no harm to anything in the intake system or the engine, adding a catch can is just something else you have to maintain.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)