Ok: The sensors AFTER the converts shouldn't make it run lousy but the wires can screw up right at them - still means new ones. You shouldn't use high heat if you are saving them but you aren't and may need to oxy/acet heat to near glowing hot to remove them - they S*CK! Then you may need to rethread the pipe too! They sell those too. Use just the sensor with the correct thread sealer that should be on ones that are OE grade, plug em in and it's done till the front two act up.
The sensors cost enough - try not to hurt the pipe! Good luck,
T
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Tom Greenleaf - MetroWest, Boston