Consistent surging

'02 civic hx 94K stick. Here's the run down. My gf's civic popped a fuel/air ratio code on day. Car still ran perfect. I could always get the engine light to shut off if I grabbed 2nd and 3rd up around 6K+ rpm. It took almost 3min exactly each time afterwards. That aside it ran fine if it came back on. Was planning on fixing it, but then I got into an accident and messed the front-end up. No motor damage, just frame cross member, bumper, hood, crap like that. Was still drivable but didn't. It got taken to a garage her family uses and when it finally got worked on, I was spending a bit of time in the clink. Anyways, they ran a diagnostic test and told her the o2 was bad. I told her they were crazy, but it got changed anyways, both u and l. When she drove it home she said it was all jerky and crap. Brought it back and was told that maybe there was a faulty one. Replaced both and still did it. Then they were baffled and that it was impossible that 2 new ones could be faulty. I told her to deal with it till I got out, and now I am. So...the moral of the story is, when you are driving with a steady foot on the gas it surges real bad. And is very consistent. Almost like there may be misfire.

My question is, how much would the fuel/air ratio play a role in this? To me it makes sense that if that is all screwed up, the motor isn't getting the right amounts of what it needs. But what throws me is that it was fine before the accident, fine after, but now junk after the garage screwed with it.

Any advice would be much appreciated. Thanks. Oh yeah, and where the hell to get the sensor. Can't find it anywhere yet