do i weld on another and which 02 senor do i buy

 

you can use one 02 by cutting the wires on the other 02 and tap it to the one your going to use.

 

if your dc has one 02 senor hole then its for an obd1 motor, just use a obd1 computer and the second o2 sensor becomes irrelavent

 

I'm assuming he's talking about a non-OBD JDM B16 which uses two non-heated (2-wire) O2 sensors in the primary collectors (the "2" part of a 4-2-1) in the header.

If you still have the stock B16 header the best thing to do is take it and your DC to a muffler shop. Have the O2 bunger on the DC welded shut and two new ones tapped in similar locations to the stock B16 piece.

 

ditto what he said, that is what i did and worked well. i got 2 castellated nuts from Trak (Trash) Auto for him to weld and cut the tip off an old O2 sensor and welded that into the old single hole.

located the two O2 bungs about 8 in. down the primaries on header pipe #1 and #3. this works very well, and was recommended by several sources plus how Honda designed them....