looking for a good plug and play option, no splicing. Dont want to pay mazda prices so what else are you guys using and where did u buy it from, thanks!

 

Bosche Single Wire O2 Sensor. AutoZone

or:

http://rx7.com/store/rx7/fdengine_maintenance.html

 

This is off topic but do you need to take the downpipe off to replace it? or can u just do it under the hood.?

 

Nope, you don't need to remove the downpipe. I typically replace it from under the car as it seems to be easier access for me. Basically, just a 5 minute job. The replacements typically come with a crimp connection already on them so you'll just have to cut the stock connector and crimp it to the new O2 sensor.