does anybody know what kind of tool you need when you unbolt the o2 sensor to take off the stock one and put on the RRM downpipe

 

either an O2 socket(side is cutout) or a line wrench works great. The line wrench has a section on it missing to get around the wire. I believe it's either 22mm or 7/8" sizes.

 

sweet...thanks a lot

 

Just an added point i'd get some penatrant or knocker-loose to spray on there a bit, let it soak in about 2-3 mins, and spray again before trying to loosen the sensor. Seems a lot of guys have some troubles with getting them to come loose.

It's as if Mitsubishi put some kindof lock-tight on there or something. The ones i've done took some work to get loose. Also after using the penetrant try warming the car up a bit. I know the pipe will be hot but it's also expanded when hot so things may come loose for you a lot easier.

 

umm yeah, when i tried takin that sob off it didnt wanna come off too easily. i finally got it out with some vice grips and a blow torch. i used the torch to heat around the sensor to expand the metal.