i had this same issue with my 2007 GS450h, sounded like a Vauxhall Astra tappets noise 😞 was gonna get it check but then it died while driving luckily i work for a Toyota dealership and they looked into it for me.
changed the high pressure fuel pump as fuel pressure was low but didn't work, then changed the in tank fuel pump and filters and problem was fixed and the tapping was gone.
been working like a dream again and i have my baby back 🙂