I have been chasing this issue for a while now. I have a 09 LNF, it was stock besides the Gm stage 1 that the original owner of the car ordered it with, I'm the 2nd owner of the car. around 65k on the car the issue started it has 71k now, the AFR gauge will sweep from 11-18 back and forth, so much so that you can feel it doing in the car now when it first started it would do it sporadically and I taped the sensor down to the charge pipe and that helped but now it's every time I start the car. I thought it was the lower MAP sensor, since the stock plastic charge pipe screw was stripped so the sensor would pop out, hence the tape, and it would do it every once in a while. I finally broke down and bought new charge pipes and an intercooler from zzp thinking it would fix the issue. when I installed it, I replaced all the sensors map sensors, mass air, o2. I put the zzp fender intake on it at the same time. fired it up and still have sweeping AFR. I than soldered the upgraded map wires since GM used those crush connectors since I have herd those can cause issues. No change. Did a boost leak test found that the map sensor on the charge pipe still leaked put the 202 O-ring on it and that sealed up the system. STILL NO change. I'm not sure what to try next, the car at idle is right at 14.7 and at WOT doing a pull its where it needs to be, but anywhere in between the AFR sweeps. any ideas?