The O2 sensors on the headers pre/post header cats... are they the identical sensors? Does anyone have the part number for them, or know where I can it? Preferably Denso sensor part numbers, car is cali spec emissions if that's important

All the o2 sensors are the same.

You can call any Autozone and get the denso part numbers. I don't think they are the same. I think the top two are the same and the bottom ones are the same.

actually theyre all different

all O2 sensors on your car have different part numbers because of the location of where its at. there is a high possibility they are all setup to read the exact same way. just because the part number allocates location does not mean it it set to read a different amount of exhaust gases

here is the autozone part locater straight to the O2 sensors for your 2000 Mitsubishi Eclipse with a 3.0L (MFI) engine

http://www.autozone.com/N,16000117//shoppi...peResultSet.htm

if you noticed the universal O2 sensor does not allocate a location. $65.99 for that verse all the other ones you decide to buy. i believe the only thing actually different is the plugs might be different. once you switch over to universal you only have cut and crimp connectors on your cars wiring once. put male connector ends on the wires on your car. if you ever have to replace your O2 sensors again. its crimp a female connector on the new O2 sensors wire, screw the O2 sensor in, and plug and play.

i really don't see why people don't always go with the universals.

Because some people don't like cutting up their wiring. Its also much easier to just unplug the old one unscrew it screw the new one in and plug it in. I do know what you mean though. When I replaced the ones on my 96 gs i bought universal ones mainly because of costs. they came with little sealed boxes that you put the wires in tightened some little knobs and it was done. Yes you had to cut your wires off and reuse the original plug but when you need to change it again you leave it hooked up to the one side and just remove the wires from the sensor to the box and put the new wires in.

as far as not wanting to cut their wires and just unplug and plug, thats a pretty expensive choice just because someones wants to be a immensely lazy! the whole job with the added in cutting takes about 5-10 minutes, or they can spend $60 dollars extra per O2 sensor and shave about 3 minutes off that. is a plug and 3 minutes of time worth $60? the first time i did a universal O2 sensor i felt dirty afterwards, because of all the money i had been ripped off for over my earlier years.