P2096 and P0137
 

Ok, I'm pulling my hair out. I had a CEL light up and it was throwing the P2096 code, so I replaced the O2 sensor myself. Took all of 10 minutes. Didn't fix the problem. I've had 2 shops look at the car and so far still no idea on the fix. One said they manually reset the fuel bank codes and that should fix it, but lasted less than a day. So I'm getting P0137 too. I know they're related and everything I've read says MAF sensor dirty, to vacuum leak, to bad sensor, to alien invasion.

And here's the odd thing. The CEL will go off once in a while and stay off for a bit, then come back on.

I'm confused and bewildered as I have not been able to correctly determine what's the cause. One shop said they wanted to do a smoke test as they believed it was a vacuum leak somewhere.

I'd like something to try and check before throwing more money at it in hopes it'll take care of the issue.

Thoughts?