SLK 32 AMG Kompessor cut out
 

I have a 32 AMG which is four years old and 36k miles. Has run perfectly until now when the Kompressor cuts out at about 4500 rpm or under very heavy acceleration (just when you need it!). Took it to MB who diagnosed a inlet pressure valve problem (B28 fault) and replaced it (for £200!). Has solved nothing. Was obvoius that they hadn't seen many 32's and didn't have a clue. Can anyone help? Tim.