Thanks for the answers and sorry if this was mentioned before. TBH it was both. The reason I first thought to be HPFP was that I used mechanic's stethoscope to rule out any abnormal noises when the engine was running in maintenance mode. I asked my missus to keep revs at about 2000 rpm and I could clearly hear the high pitch sound comming from the pump. Bought a second hand low mileage part and replaced it with all new o rings and rubber seals. To my wonder the noise from HPFP dissapeared, but the one from electric motors is still present and appears to happen exactly the same way as BigChange explained.Watched more videos on youtube with is300h or gs300h hard acceleration and heard exactly the same sound (earphones on) as it comes from my car. As for HPFP noise, found some info on american subaru and toyota forums it can be happening due to ethanol being used in the mix with petrol. Normally it goes away, if you start using higher octane petrol without ethanol mixture. But this needs to be confirmed. Sent from my SM-G928F using Tapatalk