o2 Change
 

Just changed the Oxygen Sensor and plugs. Sensor was totally Fckd up. pink and burnt, melted a bit and distorted. ive already felt a drive difference and it idles lower now.

Is there a cycle period for it. or will the computer see changes instantly?

If its upstream, you should see an immediate and a long term change. Short term fuel trim should adjust quickly, giving you a noticable difference right away, and long term trim will slowly adapt, giving you a gradual increase in mileage.

That's assuming the sensor wasn't so trashed that you were stuck in open loop. Even then though, at least LTT is used, so you still notice better drivability.

Now the question is how did your egt's get that hot to begin with?

well the pre cat had never been changed since it was installed at the factory, and that was in 02. the car has 139000 miles. i started noticing issues around 100000 miles, and the mileage got worse, and idling got high, rough starts. mileage was getting worse and at points id through a qtr tank in basically 2 days, only driving 25-30miles. so i thought, yea nows the time to get it done, and i did the plugs too even tho they werent terrible, they were done during september i figured though the hoods open why not do em

thats about how bad mine were i changed out mine at 115k or so but still have the service vehicle soon for cat converter not operating efficiently but when they put the new cat on and the new o2 sensor they striped the threads so now i can see exhaust gas leaking around the o2 sensor that my be throwing the code