Last weekend I replaced my MAP sensor and did a tune up with new plugs, wires, cap and rotor. Today I replaced both upstream O2 sensors on my Dakota today. I ordered the OE parts from NGK. I had no CEL on, I just did it as maintenance and to hopefully improve my MPG and if I get a little more power, that will be good too. I have 110,500 miles and was still running the original O2's. I did a test drive, truck seems to run a little stronger and had a smoother idle. Question is, can you tell much about the engine's condtion by the condition of the sensor ends? They were both white to whitish-gray color. The holes in the business ends of the sensor were all clear and unobstructed. I know with spark plugs if they are white you are running too lean. Does it mean the same with an O2 or is it normal? Thanks for any info you may have.