Without the ability to modify your tune (inj pulsewidths or duty cycle) in open loop, I'm afraid the corrections to the learned adaptives (LTFT) by the addition of larger injectors will cause any WOT lean condition to be worsened. As you are seeing, the PCM is pulling fuel during closed-loop puttering around to compensate for a larger injector. Once this correction becomes "commited to memory" it will continue to use that compensation in open-loop (WOT), reducing your fuel PW's. If you were rich before at WOT then it's a good thing.....