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looks like california emissions uses two different part number o2 sensors. Federal uses the same sensor before and after cat.


If yours is a Cali emmisioned rig, that would explain why you are having to re-use the old connection. When you do cut and solder, make sure to keep the new O2 senors wires the same lentgh as the old ones, a longer/shorter distance the signal has to go can/will cause the ecu to get different readings from what it expects, due to the difference in signal strentgh.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed