After installing downpipe on my 2015 audi a3 i haven't seen a CEL until yesterday (week after installing DP) and now getting the check engine light with it say O2 sensor heater control circuit bank 1 sensor is that normal or something separate from the downpipe install???? Im definitely considering putting back my stock DP cat bcuz it's WAY too loud and everyone here's me coming and I'm not sure I see a difference in hp.