So I had these two codes show up over the last two weeks and have researched all potential fixes from cleaning/replacing maf, O2 sensors, pcv valve, vac lines, ect.
First I visually checked all vac lines. Nothing. Cleaned maf. Still threw codes. Replaced pcv. Codes came back again. Ordered set of x4 O2 sensors, waited arrival (and then procrastinated the replacement because they're a b**** to work on) I decided to thoroughly check vac lines by pulling them off and seeing if there was anything hiding from me.
Since there is a line at the back of the intake manifold I took off the upper plenum and found a split in the gasket that separates it from the lower plenum. The split is between two runners... not between a runner and where ambient air can get in. So I replaced it put everything back.
After 200mi and new O2 sensors still in their unopened box, no codes. What gives?? Not complaining, but utterly confused. Why would two intake runners sharing the same air throw lean air codes for both cyl banks?