Main o2 sensors. here's
the ones i used, and i also found is a code that gets yout 20% off your first order from sparkplugs.com might as well buy some more stuff while you're at it.
go to autozone and get an oxygen sensor tool, they give you tools for free, you pay upfront then return it and get your money back, get some pb blaster cz they'll be baked pretty well in there, spray it, let it sit, make sure all the engine parts are cool too, then take the sensors out, use the awesome crimps that come with the kit and put the old plugs on the new sensor. the kit comes with great directions and tell you everything you need to do. code rid of my code 25, car uses a little less gas now and no more weird odor.