It is much easier to weld a bung with the DP off the car especially if you aren't the one doing it. I'd charge you less if it was off the car. I'd wait. Yes they can weld the bung off the car if you are installing it near the stock bung. It just depends on where you want the bung. This is what innovate recommends.
Install the oxygen sensor’s bung upstream from the catalytic converter (a bung and plug is
included in the LC-1 kit). Any decent muffler or exhaust shop can do this for you. The wideband oxygen sensor is then installed into the bung to take a reading. (Insert the plug into the
bung when not in use). The bung must be installed in the exhaust pipe at the side or on
top, NOT on the bottom of the exhaust pipe. Best position is between 10:00 and 2:00
On TURBO CHARGED vehicles:
Install the bung downstream from the turbo before the catalytic converter. The high exhaust
pressure before the turbo interferes with the lambda measurement and the high exhaust
temperatures encountered there can damage the sensor.
Do NOT install the Bung below the 3 o'clock or 9 o'clock position.
Condensation can form in the exhaust pipe and permanently damage the sensor.
6 o’clock is the absolute worst position to mount the sensor.
Wide band oxygen sensors – like the one shipped optionally with the LC-1
– are designed to work with unleaded gasoline. Using them with leaded gasoline
will significantly reduce the lifespan of the sensor. The reduction is directly
proportional to the metal content of the fuel. In most cases, a wide band sensor
will provide accurate measurements somewhere between 50 hours and 500 hours
with leaded fuel.
WHEN INSTALLED IN THE EXHAUST, THE OXYGEN SENSOR
MUST BE CONNECTED AND OPERATING WITH THE LC-1
WHENEVER THE CAR IS RUNNING. AN UN-POWERED OXYGEN
SENSOR WILL BE DAMAGED WHEN EXPOSED TO EXHAUST GAS.