norcalrallyist

I am currently having a problem passing the emissions test here in TX. I decided I would try replacing the o2 sensor and then retest but Ive run into a big problem. The old o2 sensor came out badly and stripped some of the threads and Im not able to thread the new o2 sensor. I tried using a chaser tool to straighten out the threads but that didnt work. Should I use a helicoil now or maybe a tap? The threads inside the exhaust manifold are still look ok deeper into the manifold but the threads at the beginning are totally ruined. MY car is a MY94 WRX

Thanks,
Garrett