It doesn't need a rebuild at all, did they even bother to check the fuel rail pressure ?
It sounds like a classic fuel pump failure to me, these will surge violently sometimes, I've just replaced my own pump for the same reason, it was surging from 0.5 bar to just over 3 bar, absolutely rythmically idle was going from around 500rpm to 2500rpm, the pump sounded 100% PERFECT, it was not until I put the gauge on there that I confirmed my suspicion.
Your readings are all around the same, no1 is a bit low in comparison, but could just be a simple error with the tester.
DON'T take the engine apart, check your fuel pressure, renew the pump/filter, rewire it and the fans also if not already done so.
tabetha