A boost leak, bad air flow meter, leaking bypass valve aka blow off valve are all possibilities. There's also the possibility that the fuel pump resistor relay is failing althought it usually either works or flat out dies.
The wastegate isn't the issue. A bad wastegate will have you seeing spikes and hitting fuel cut not the other way around. If it were to fail open you'd see low boost across the board on top of the lag.
Fouled plugs, improper spark plug gap, bad high tension wires, oil causing a misfire or improper mechanical or ignition timing could also cause this.
It's all really easy stuff to check and shouldn't take long to work through the list. With the BPV/BOV just pull it and plug the ports on each side with a rubber cork and hose clamp from the hardware store to see if the problem goes away.
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