Well I was in the process of installing new cams in my 03 CLK 5.5 amg. And I had notice this before ,but really did look at it , as a problem ! until I pulled the valve covers.
The fuel line that feeds the injector fuel rail , makes a hard bend at the rear of the motor , against the fire wall. It sits just above the Hot exhaust . Is covered with a nice S.S. braided and I think it has a teflon inter hose . It appears that the heat may have deformed the interhose. It will not become unkinked?? Bend it back open and the flow will increase. Well a new one is being made and it will have a thermo shield covering over it .

Is there somewhere on the line where it says "Don't kink hose!"?

Nope. and surly under normal performance of the stock engine , it meets or exceeds what is needed to supply the mtr. BUT as we increase the output of our engines . through modding. . we must ensure proper supply of the increase needed fuel , to meet these new requirements. Do not want to defy the laws of physics , proper air & fuel ratios needed to make more HP.