What is also possible may be the most obvious. Did you also clean all the hoses attached to the intake / induction system? Did you clean them inside and out? Did they fit tightly and the clamps (where needed) were snug? The clamps, hoses and gaskets were all cleaned and in good shape?

I had a vinyl vacuum line split going to the EVAP system. I had a huge hole of power WOT between 2500 and 3500. Mind you, my rig is N.A., but sounds like a big leak from here.

Just throwing this out, worth checking.

Mike