If it's not just at specific speeds then it's unlikely to be O2 sensor or boost issues, more likely Coilpacks or AFM/MAF, and these are problems which cost nothing but an hours work to prove or disprove. Even if it's not the solder joints on the AFM it soon would be so nothing lost.
Coilpacks, remove and clean then spray or soak in WD40 and try again, only a short term fix but again costs nothing but an hours work.
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