I am replacing all four of my O2 sensors.  I ordered some off of ebay.  The pre-cat ones were the correct oval plug, but the post cat ones came with the square plug.  Mine are all oval plugs.  I have looked at Mike Focke's O2 page and he has:
986-606-127-01 2000-2002 in front of the starter catalytic-converter
986-606-128-01 2000-2002 after the starter catalytic-converter
The one I bought that fit the pre-cat is the above part number.  I can't find the 986-606-128-01 part for around the same price.  My question is can I use the 986-606-127-01 part for post cat?  Is there a true difference in the parts?
I appreciate any help.
Thanks,
Chris