I think I found it in this diagram as
part 74, A1244710681, which then seems to be guiding overflow diesel
or vapor to the surroundings (sits after a valve);
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=124130%5F15S&M=603%2E912&GA=722%2E415&GM=717%2E433&CT=F&cat=15S&SID=47&SGR=015&SGN=01
The effect on your car will be diesel flowing on things it should
not instead on the ground, and nothing to do with performance.
br,
syljua