there is good luck with the mechanical fix on the 04's, seems the ECU figures out that you resistored it and will still set a code..however, with the two nofoulers, it stays off.
here is the link to the do it yourself fix, not that hard, and costs about three dollars at Radio Shack,
http://www.dooleyprinting.com/brsc/O2_CEL_FIX.pdf
the mechanical fix is a little more involved in the making, but it involves purchasing two No-foulers from the HELP! section of your local auto parts store, but you need the 18mm ones, like for an old Ford.
take a 1/2" drill bit and ream the hole out in one of them, then take the larger one and screw it into the other one. then simply screw that into the rear O2 sensor bung, and screw the O2 into it.
sometimes, depending on DP maker, you have clearance issues with the floorpan.
that help?