weld in the bung. if you look at the downpipe, there is a dip where it goes down and then comes back up. this is the spot some people don't like because if you look under the car, it comes down lower than some people are comfortable with. some people just leave like it is, other people cut out the interlock flex section and weld in a shorter section. it is really just preference, as far as I know, no one has ever had ground clearance issues with that section of downpipe, but my memory isn't the best sometimes.
it seems like someone said you couldn't cut the o2 sensor wires and solder in longer ones, but that's what I did the last time, and it seems to be working just fine.
if you haven't installed a wideband sensor and plan on it, read the directions on where to locate the sensor in the exhaust because it will need to be in the downpipe pre cat converter, and you might have an easier time welding in the bung at the same time as the oem o2 sensor.
