YIPEEEEE!!!! SUCCESS!!!!! It was a busted vacuum hose. I found the most excellent place that works on Mercedez. They were packed with cars but I was there for less than an hour and because of discounts from their website, I paid only $60 for the whole thing. I feel so much better having found these people. They couldn't do the inspection, though, because the codes have to go through the re-set cycle again. He said 100 miles. I'm certain that it'll pass inspection next time, though. This is such a load off my mind.

Thanks again to all of you for your invaluable help. I'm so happeeeeee!!!!!