The dealer is....of course....trying to feed you a bunch of crap.. The Bosch pump is the same for MB and Chrysler...

Check all the hoses and make sure they are tight and no cracks... you can try flexing the hoses while running (CAREFULLY) and see if you can induce the CEL... it sounds like you have and intermittant leak and this may help find where....

I have had the large hose coming off the air pump pop off once and I knocked the line to one of the vaccume switches off while under the hood and didnt notice it till I got the CEL...