so its not at any particular rpm, but more so when the engine is under load?
I think it could be:
Could be the air volumes being measured by the ecu are wrong, this being caused by a boost leak or a fault in an electrical component (AFM, AAC, O2). either way, the air thats getting pumped thru the engine isnt matching what the ecu is reading. I dont think it would be a dirty pod filter or a collapsing pipe between the AFM and turbo because you're making full boost.
OR
Fuel system problem. when the engine demands alot more fuel when on increased boost from cruising or idle, the fuel pump might be bad and not be keeping up, or the lines/filters might be partially blocked only allowing enough fuel thru for idle and cruise mode....
So I'd check: AFM, O2 sensor, AAC valve - these bits you may have cleaned but could they just be broken? Fuel pump, all fuel lines, fuel filters, fuel injectors. All air lines and hose clamps, fuel pressure reg. to plenum line in particular. Alot of this shit you've done so on goes the process of elimination!
hope i could help
cheers
rb25