http://berktechnology.com/index.html
I noticed that you guys were talking about this part. It already has the o2 sensor on with it, right? but what about the o2 sensor on the end of exhaust? will that o2 sensor be ok with no cat or??

 

it comes with a mechanical o2 sensor to trick the sensor so you dont get a CEL

 

You are confusing an "O2 sensor" with the "mechanical O2 simulator", which is that little side tube sticking out of the t.pipe. You still screw your existing O2 sensor into that little tube. This takes the sensor far enough away from the flow of exhaust gases that it will "fool" the ECU into thinking that you still have a cat.

An aside: I look at that link and see the picture of the Berk t.pipe. I recall when Berk first brought out their t.pipe that quite a few owners were still reporting CELs. When this was brought up, the Berk rep posted up that "there is nothing wrong with their product". That first product had that little tube angled so that it pointed towards the incoming exhaust flow. Funny how this latest version has that tube at perpendicular to the main pipe. Coincidence?

 

Also I have a fairly new Berk test pipe and after a few miles I threw CEL. installed anti-foulers and it has been off for almost a year. A friend bought one before I got mine and never threw CEL

I think its a crap shoot, but even if CEL comes on its an easy fix