I replaced the O2 sensors (2-CA truck) with OEM ones, which surprisingly came from Schucks. I can't remember the exact codes that I pulled, but I have a commercial code reader (it is just a commercial device that shorts the T1 and E1 connectors together. The book that came with it indicated that the codes are for running rich first, and then running lean afterward. I did lose some power, but around the same time I had to replace my tires (31-10.5-15) with some slightly wider ones (31-12.5-15) and I didn't think that the power loss could be attributed to something else. The significant loss of fuel economy was what concerned me above all. I mean my truck can still get up to highway speeds, but I need to push the pedal that much more. The power loss was most noticable when I am in 4-HI. My top speed in 4-HI used to be 50mph. The last time that I had to run in 4-HI was in January and my top speed was like 35-40. I am weighing my options right now between rebuilding the 3.0, swapping to a 3.4, or the Tacoma 2.7, or just selling the truck and getting an older Toyota with the 4 cylinder. I have all the time in the world to ponder this since I won't be back home for a little while longer. (I am on deployment in SE Asia at sea right now) Thanks for the replies, and if you have any other great ideas, please share them. Thanks.