Im doing a tune up on the Formy. The cat is removed, but the computer hasnt been tuned yet. Do I need to replace the rear o2 sensor, or no since all it does is monitor the cat correct? The front should be enough since it will be tuned out in the next 2 months or so, right?

 

Yea the ones behind the cat are just for checking if the cat is doing its job. I wouldn't change it if you are just going to tune it out soon.

 

Your 1994 is OBD-I and does not use "after-cat" O2 sensors. They were added in 1996 as part of OBD-II. You realize you have two pre-cat sensors, one on each bank of the engine.