[Jared.FR-S]

So I am starting to get into cars (I’m a noob!) and I own a ‘13 FR-S.
A few problems I am having with it:
-Squealing noise when I start it up in the morning (30-45 degrees) not sure what it is??
-Check engine light, says it’s the o2 sensor, the o2 sensor has been replaced twice and it’s burned them up. I do not have a header but I do have a Borla axle-back exhaust on it ( pretty sure, haven’t jacked it up to see what exactly is going on under it ) . I got the car modified like this and not sure if it was tuned... or if it even needs a tune. I’ve been to multiple mechanics