2013 Cadillac ATS 2.0t just put a big front mount and one of the oversized turbo on it and working on tune been fine and all of a sudden it goes pig rich. Spitting won't run wideband showing 9.8 so way rich. At idle cruising doesn't matter. Get home and check log as luckily was logging data and noticed everything was normal but o2 sensor was staying locked at 1.275 for a while then started switching looked normal then dropped to 0 and never recovered. It was only going up to around 100 tops and falling back to 12 or so. Then noticed no movement what so ever on long and short term fuel trims both stuck at zero. Once the short shot up to 18% then back to zero.

Now on a prievious log I had been really lean and it shuttered hard when laid into it around 50mph saw it drop lean so before I let out it shuttered. When checked my log it spiked way lean on wideband was 20.9 like free air and was wot on data still guess was right when I lifted. The narrow band was reading nothing at that point. Like it was dead. Prior to that was switching so like it just dropped dead. So is the o2 dead and causing all these weird issues or is something else making the sensor read zero and very low? Will say wide band is staying around 13.7 to 12.9 cruising not right but not like the narrow band that is around 15-25 at that point.

Car has 30k on it Maybe when I first switched to big turbo I killed it going lean on it? I had a horrible lean pop blew the throttle body pipe off on my first drive just not enough pe yet. Didn't realize how much it was going to need for changes to turbo. Where stock would hit 24lbs this one is 30lbs same setting so had to back all my boost tables back to near Stock settings where car saw 18lbs the larger sees 22 -24 lbs same settings. So I just under estimated the difference it was going to make on my first trial tune and run.
Hope it's just an o2 sensor and not some weird issue I have some how caused. I did check all connections reseated computer plugs and even cleaned my sensors maf and o2 to be sure wasn't something easy. Thanks in advance for any help