Sorry - missed your reply above. Basically a short term fuel trim is an instant adjustment for current conditions (based on the lean/stoic/rich signal it's getting from the oxygen sensor). If the PCM finds it is continually adding or subtracting fuel from the base, then it adjusts long term trims. They adjust quite quickly though. Long term fuel trims should be within +/- 5 percent or so. When you say you have loaded in the stock file, do you mean the actual stock file? If so, that will run rich if it isn't know you have bigger injectors (or they deliver more fuel for a given opening time) Could be that the oxygen sensor was part of your problem but not all of it. I had a minor boost leak and a failed actuator a little while ago - made troubleshooting very difficult. Check the fuel trims and see what they say. If you had it tuned, I'd give your tuner a call too and see what they say. Or if you want a second opinion, most places will do a few dyno pull for Les than $200 and would hook up a wideband. A reputable place should be able to tell you if the tune is ok or not. Could still be mechanical too, like a failed fuel pressure reg or blocked fuel return line.