when removing a stock muffler and relocating a borla to that vacant space behind the catalytic converter. Should I cut off the piping right after the new muffler or leave the piping to continue to the rear?

 

I'd run it out the rear. Leaving an open exhaust pipe under the vehicle can only cause CO2 to enter the cab. Not good.

 

it also makes it really loud in the cabbin, you get that annoying drone sound.

 

I've seen it done both ways.

 

I would make it go out the rear. My buddy had his dump out right under the drivers seat and you couldnt hear anything the entire time he was driving, although he had no muffler . You wont get sick of the drone if its at the back of the Jeep.

 

People run it both ways. The drone that people talk about is more a factor of the muffler you choose than where you terminate the exhaust. I run a Dynomax muffler that dumps out in front of the rear axle and I have no drone.

As far as CO gas entering the vehicle, this is really a non-issue. Our vehicles have lots of ground clearance, i.e. lots of air ventilation under the vehicle. Also modern vehicles are very air tight. There are just not enough openings in the vehicle to allow CO to enter.

People usually terminate the exhaust underneath the vehicle for a reason. Some that come to mind are EVO MFG EVOLever Rear Coil Over System and GenRights Aux fuel tank.

All that said, if you don’t have a reason to terminate the exhaust underneath the vehicle I would just run it out the back.