running rich on right bank

[dastang2]

i have been running rich on the right bank and the codes said the header o2 sensor was a problem. and i notice my temp. gauge is fluxuating all over the place and my fan is not turning on unless i unplug the sensor. if i took out these old sensors and let the air touch them will it screw them up. i have another o2 sensor and a fan switch to put back in it but will a 180 thermostat make this engine run rich on 3 cylinders. i don't think only 3 would flood out if that was the prob. will an exhaust leak cause this. i have one now where the header meets the pipe on the right side close to the sensor that is screwed. could that be making this thing read wrong. and if i had a broken intake bolt in between 2 tight bolts with silicone all over it to seal better would that make it run rich on one side or both. it is broken off on the head on the right side. would that make it run lean or rich. it is a 95 5 spd