My neighbour's Merc ( 2005 270 cdi E class ) has gone into limp mode and every now and again the engine light comes on.
I told them to get the codes read and then i would have a look, They took it to a garage and had the codes read - Intake channel shut off was the fault showing.

i had a quick look on the net and it seems common, but couldn't find the location or a picture. I'm having a look at the car tomorrow but just wondered if anyone has any info before i start pulling bits off lol.