This has little to no effect on engine performance from what we can tell. And Clim is correct in his explanation.

We have received no lights or codes, but had one SLK32 report a NO Secondary AIR code (not sure on number). It didn't effect the car, just came up on a scan.

This is more of a an astethic mod and for a car that is daily driven or under warranty, I really would not suggest it.