Engine code P-0171 coming up, possible O2 sensor?

That is a lean fuel system and a stolen computer wouldnt'really affect it at least for that code. Check your fuel pressureit should be 44.2-54.2 psi. If it is below that then suspect a pump. Also check for a vacuum leak at intake. Spray some choke cleaner around intake and throttle body. But check the fuel pressure first.

I meantconverter not computer, error on my part. P0171 is a lean condition which your O2 sensor will pick up when you don't have enough fuel pressre and your injectors make the engine run lean due to fuel starvation or not enough fuel. Or a vacuum leak will cause this as well or a large hose off of the engine as the computer will enrichen the fuel load as much as it can. The diagnosis is fairly correct with the information that is given. Check your fuel pressure this may be a problem with the pump or a clogged fuel filter. Either of any the things i've given you can cause this, not an O2 sensor. If you absolutely feel it's the O2 sensor then replace it and you'll end up with teh same code. What is your fuel pressure. It can also be an injector problem as well.