With injectors, using M4. 4 and tuner pro you can edit the tune to suit injectors, oranges run a constant of 1.000 and my greens run something like 0.7800, with the constant being lower to adapt to the larger flow injectors.
So if you are running greens with the constant set for oranges, it will be over fueling, this is not getting into dead times which will also have an effect.
With it running rich your long and short term fuel trims will be out, with the ecu trying its best to get it close to stoich, as example your trims may be something like - 20% as the ecu tries to accommodate for the larger green injectors and the settings it has for oranges, so now that you have swapped back, it will, for awhile anyways remember the trims and still be following that, which is why you have seen some leaner running now you changed back.
Either pull the ecu fully with the batt disconnected to clear the trims, or just drive it for ages and let it learn again.
