Have a ticking noise from engine. Wife has had the 2017 sonic turbo for 5 years and says it has always been there. I only hear it at idle sometimes it sounds much louder then other and sometimes at idle I don't hear it at all? Recently had a P0420 code that I cleared by changing the flex pipe ( was broken) and rear cat as well as both 02 sensors with Bosch ones car is running much better. But still the annoying ticking . Could it be a knock sensor going bad? The car runs lean LTFT at idle about 25 and neg 2 -5 STFT. There is no DTC now? The timing is about 5 degrees so I am good there too??? Any suggestions or experience is this ticking ok ?