I a 97 sunfire with a 2.4, today I got a p0133 code. It turned out it was my gaskets before the o2 sensor the rksport header. I hooked up my scantool software and my o2 senser is all over the place at idle the volts are .8 to .050 to .875 and the si feul were +2.3 to +10.9 to -0.8. Is my o2 senser bad, or is this normal. It would make sense because my gas mileage is between 16-18 mpg in the city

thats what the narrowband o2 does. it fluctuates up and down.