Since the dawn of MSI in 1999 or so, I've used the following pair of
components to clean up registry on removal of my product(s).  For  the
life of me, I can't come up with the correct WIX v3 syntax to do
this.

Can anyone help?

Here is what the 2 components look like in Orca:

Component               ID      Directory       Attr    KeyPath
REG_HKLM_Cleanup        {guid1} INSTALLDIR      4       REG_HKLM_Cleanup
REG_HKCU_Cleanup        {guid2} INSTALLDIR      4       REG_HKCU_Cleanup

Registry                Root    Key             Name    Component
REG_HKLM_Cleanup        2       SOFTWARE\MYApp  -       REG_HKLM_Cleanup
REG_HKCU_Cleanup        1       Software\MYApp  -       REG_HKCU_Cleanup

TIA, Jim