Recently I've noticed black dust buildup on the rear bumper and around the rear quarters. I can't pinpoint when I first noticed this.
This is a 2014 5.0 tvs car with a vmp tune and has been essentially unchanged for four years. I run pump fuel with 4oz boostane additive per tank and have an offroad H pipe with stock headers and a borla touring exhaust. The car seems to run fine and I can't tell any obvious difference as of late. WOT logs from a couple months ago looked OK Lambda was 0.78-0.80.
While there are other possible explanations I would like to exclude a rich run condition during idle and normal cruise. Can someone please let me know what monitors I should watch when logging and what would be a red flag for rich result? I can log 30 seconds of idle, normal acceleration from a light up to 50mph, and 30 seconds of 40mph cruise.
Thank you.