240 exhaust problem used to have cat

[bear]

i have a 91 240gl, some time ago the cat went faulty and somebody has fitted an exhaust with what looks like a hole drilled in it where the sensor is fitted. the problem i have is that the down pipe is blowing and i am unable to source a down pipe with a place to fit the sensor.
could i fit a normal exhaust without the sensor.

[arete]

I have an 81 240 and have replaced the exhaust manifold as well as that down pipe. W/O the sensor your car will run poorly. I got my parts at a wrecking yard. If your current setup is blowing out that O2 hole, why won't a sensor screw back in? I think you can plug that hole with any bolt, but you need that to run correctly.