[djmcmath]

Too lean could very well be a vacuum leak post-MAF. Try the old carb cleaner trick to see if you can identify anything. If that fails, it isn't necessarily not a vacuum leak, it could still be one that's hard to find. Fuel pump starting to fail would cause fuel pressure to be less than calculated, depending on where your system senses pressure at. Oxygen sensors typically tell you when they're bad, don't they? I know that mine gave "out of range" errors when they started going out.