Twinchargedlsx

So I've been working on a lean condition for some time now. I think it might be 02s but not positive... It'll run a 13-14 AFR in open loop when I first start it but once it goes to closed loop the stfts go to -20+ on both banks and make it idle at 17+ AFR. If I give it some gas then it goes back to 13 range. And if I command a 14 afr with the scanner it runs 10x better and holds a decent afr and the stfts go to 0. It's a turbocharged 416 ls3. Cam, 102mm throttle body, CNC aftermarket heads, Holley high ram intake.