These codes came up at samectime and I took it to a chev dealer. They replaced the cam cover for a leaking PVC valve. Then rechecked the fuel trims as normal. I know the PVC was bad by doing the finger on/off test over the opening in the diagram.
Same codes came back 1 day later and the car is back in the chev dealer. I am waiting too here back. They did mention the front crankshaft seal. Is it possible to get a vacuum leak from this seal. I always assumed the base was under pressure.
Could it be related to the evap system. Perhaps the purge valve? Any input appreciated.