the o2 sensor is placed on a small 8 inch long pipe that comes before the cat and after the header downpipe. the exhaust should have nothing to do with the o2 sensor. here is the order if you are confused.

header, small 8 inch pipe with o2 sensor attached, catalytic converter, and your exhaust piping and muffler.


your car is obd1 so you dont have a second o2 sensor after the cat so no need to worry. you only have the one in front of it. i replaced everything with dc cc header, carsound cat, and RS*R catback by myself so i know it pretty well. i also did the work by myself, with no help, in 5 hours. pretty good for a first timer i believe.