Wanted to wait and see if this was the problem and now can confirm it is.
If you are running the stock headers with this kit check the state of your precat. I've been working with Zach at CSG on my tune. Everything was dialed in except for a very rich condition and stumble when leaving a stop in first gear. Only showed up under low flow conditions below 1400 rpm. Tried swapping the AFR sensor, made it a little better but didn't get rid of it. Zach eventually got me a map that worked but he had to do a custom map that takes the car out of closed loop in that area. I switched to a Tomei header over the weekend and all the issues are gone.
The image below is a boroscope pic of the precat. The cat material is failing and clogged in about the middle 20% and it changed the flow enough that the reported AFR was reading very rich and making the car stumble when the closed loop system overcompensated, sending the AFR to 16 or so. These precats aren't designed for the higher heat from this kit.
