My check engine light wont go off.. i have

Take it to autozone to get it reset and see if codes are still there But write down any additional codes you find, also if you bought a after market 02 sensor it may not be hooked up right. I have had this problem with after market 02 sensors for the past year. Bad batch and it does happen, once engine has been shut off and ran three times it should have went off by now.

can take up to 125 miles to reset

I own a 97 with just at 297,000 miles best car ever. my engine light was on for about 10 months,but like you my car ran fine, "i am in the auto biz 20yrs so always check your warning lights out asap" so i pulled a code wich said o2sensor and no other codes were present, i replaced sensor "dont remember wich bank it was" but that didnt turn off light, so i hooked scanner back up and then i received a new code...PO401-EGR FLOW INSUFFICIENT.the part was pricy and in most cases can be cleaned, so after almost 300k o2sensor and egr flow,neither of wich affects drive "gas milage" but thats all.also traction controll light stayed on but system was fine,so lights on a lexus 90% of time are emmisions issues. my car is still running perfect"make sure to change timming" and roll.