I did an oil change on my 3.9(280'km) and used a top end all sing you butte Penrite oil, bad move.
Same as yours I had the oil light on longer at start up and rattling in the lifters.
I swapped back to a basic Castrol oil, oil light out straight away and after a few days all went quite(only2X 6min runs a day to work).
Your flush may have freed up the lifters but my experience as above is it could take a little time to settle.

