Bought this product after installing Red Star 200 cell Downpipe to replace a failing OEM catalytic converter in my stage 2 GLC 43 AMG. Unfortunately, the downpipe caused a check engine light, so I decided to use a spacer to resolve the problem. A word of caution: I noticed that if I drove under 2000 RPM on average with the spacer, I would get a code for exhaust leak/excessive oxygen. So I decided to drive the car at relatively higher RPMs to produce more CO2 to normalize the parameters. This was all done while flashed to stock. After clearing the pending codes and driving the car more aggressively for 150 miles or so, no code ever came back. All monitors were ready for emissions, excluding EVAP. So if anyone is getting codes about the o2 sensor/running too much oxygen, consider driving the car at relatively higher RPMs to activate the o2 sensors that are not getting adequate readings of C02 emissions. I will be using Uro Tuning for many other tuning needs!