Hi,
We have a 1996 C180, we had a problem where when the car was idle, it seemed like it was miss firing and when you put your foot down it spluttered. whilst on the road anything above 70mph you wouldn't know there was a problem, but overtaking and increasing the revs it struggled.
We took our car to our local dealer, they found that the Lamba Sensor was knackered, it cost us £90 plus VAT and labour, total bill was £245.00, expensive iI know, but it runs like a dream now!

Hope this helps,

Lisa