Headers and no cats will cause issues.Ok i see part of your problem,prochargers tune is not meant to be run with longtubes and no cats,unless u had them do something just for your setup.Could be why your running so rich.I would contact procharger tech,he is always on here,that or custom tune.
So from the looks of it, it's the tune? It was running perfect before just started doing that. I've put about 1500 miles on it.Headers and no cats will cause issues.
Our tune was based around stock exhaust, and cats.
Lambda will move around, but hover in the .78-.82 lambda area under WOT.