With our 1.6 SX4 from 3/2008 the middle tube has to be changed in front of the end pot (still good condition). Was with the friendly on the stage and looked at the Malheur. Part of the middle tube is a cat which is flanged at the front to the pipe coming from the Krummer or main cat. This main cat also has the necessary two lambda probes for controlling and controlling the exhaust flow. The integrated in the middle tube 2. Kat has no probes. Now the Freundl separates I remove the defective center tube after the cat by means of flex and mount a new center tube with bells. Thus, the expensive purchase of the 2nd cat is spared. Nevertheless, the question arises to me about the meaning of the 2nd cat? Does someone happen to know?