1st Gen R53 Cooper S Most liked posts in thread: Header question - primary o2 bung

I have wondered that myself, I know alot of the o2 simulators have spacers to pull them out of the stream as well.
O2 Sensor Mini Catalytic Converter

O2 Spacer [O2] - $11.97 : Innovative Performance + Customs, Manual Boost Controllers - O2 Sensor Simulators - Performance Accessories