Just because it's not listed as an individual item in BMW diagram does not necessary means that it's not there. BMW has a habit of not listing individual item for certain part, but list it as a whole unit instead because they consider it as non serviceable part. One obvious example is headlight adjuster. For pre facelift, you can get the part, but for facelift/angel eye, it's not listed at all and we all know that it's there..
BTW..back to the topic, after talking to the owner, it seems that he has a sluggish acceleration problem..according to him, all sensors were replaced not long ago with genuine BMW parts. In this case, I agree with the other poster regarding the catcon being clogged.