i purchased and install a new 3 wire heated o2 for my truck. reading from the internet, i discovered all o2 are very common except for the plug connectors. using this advice i ordered 2ea volvo bosch 02's from ebay for 15 bucks each. i installed one this weekend and it works great and enters closed loop very quickly and stays there even at idle. why pay big bucks at the dealer when ebay has for cheap.

 

http://www.goautocenter.com/super_deals.htm
$20 for a 4 wire (4th wire used to ground the sensor, not really needed).
That's new in a box from a dealer