Note for you 93 ZJ owners with O2 sensor problems.
 

I found a real nice suprise when doing the header.

The O2 harness runs up past the oil pan then gets held
to the block with a loose clamp.
http://members.cox.net/wilsond/temp/holddown.jpg

Look at what engine heat did to the wire inside that
clamp.

http://members.cox.net/wilsond/temp/damage.jpg

That explains a lot as to why the sensor checked out
ok (from the sensor connection) but still wasn't reading
right on the DRB.

Wire and solder should fix this but I've got to find
a better route for that wire.

--
DougW