Exhaust /O2 sensor question

[gwynethh]

After doing a bunch of suspension work we finally got to move the SVX and discovered an exhaust issue.
Last fall we thought one half (P/S) of the muffler was not passing any gas based on under tip moisture and direct feel. This spring neither side did. Car ran with a big gas leak somewhere. We noted hornets clustering around/entering one tip after our test trip of 200 feet or so. So something plugging the system?

We have a used Stebro system complete from the headers back. System is welded and was cut out about 3" back from the cat. We plan to join it with a coupling and clamps.

We have a 1995 OBD1 system. Exhaust has only two O2 sensors forward of the pre-cats. No other sensors or bungs. No sensor in the cat.

So will we get any CEL codes?
Is it hard to unplug the O2 sensor wiring?