in my case 98 Ford Ranger, 110,000 miles , 4.0 V6 had the error Bank 1 and bank 2 running too lean. Replaced the upper intake(plenum) gaskets. the gasket rings in the plastic upper intake. did not remove the fuel distribution manifold. took some time to disconnect things, not too bad. EGR tube bends forward inside the manifold so lifting the plastic maniflod and shifting it forward to get it disconnected.
got it all back together. Seems to have done the trick. CEL has been off for a few weeks now.

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1998 xlt 4.0 Ranger