My old front o2 was switching very slowly when I hooked up my scanner and viewed live data. I went to autozone and got the Bosch 15738 Universal fit for $80. I didn't use the crappy splice connector that comes with it. I have had problems on others cars as well when using the supplied connector. I butt jointed the wires and soldered them.

The o2 is now switching at a normal rate and I put about 100 miles on it today and am now getting almost 27mpg where before I was only getting around 22-23mpg on the interstate.