After chasing down vacuum leaks, etc. I finally got rid of the lean codes when I blasted the injectors with tons of cleaner. Injectors that are slightly dirty will not deliver the fuel it needs. This will make the engine knock a bit too because lean mixtures detonate instead of producing a smooth flame travel. My car will once again run on 87 without fussing. I used 2 cans of B-12 at once and one more later when I noticed it was helping.
