tune or o2 sensor
It's hard to say anything about the tune, but which O2s are you talking about. You don't need the rear ones at all. It won't effect the tune or power in any way.
If you don't have front ones, then that may be part of your problem.
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Here's the thing about having no O2 sensors. It's perfectly fine to go without them, as long as the tune is right. So put the wideband in get the AFR close in all areas and you're good. The downside is if the weather changes much the tune will be off again.
I run my car in open loop speed density (no O2s, no MAF) all of the time. And I usually keep the wideband in at most of the time as well. During the winter, sometimes it would be a little rich and other it would be a little lean. Not enough either way to warrant a change in the tune though, but now that its starting to get pretty hot some days, I've notice that it's a bit on the lean side. A few minutes of logging and tuning and I'm back to normal.
If you drive the car a lot, it would probably be easier for you just to eventually stick some O2s back in the fronts, but it's not really necessary for right now. You can't use them while your tuning anyway and they're expensive as hell.





