Lifters.
Stuck or own out. Even one stuck lifter can make lots of noise.
See my thread and solution here -
https://www.volvoforums.org.uk/showt...=246575&page=4
I used FAI lifters, which where lot cheaper as local brand, but bit noisy, when car is warmed up.
INA are used as genuine on this engine, if you open up your engine, you will find them in there.
I've been told RUVILLE and KOLBENSHMITD are most quiet and more expensive.
Don't forget
new injector seals and maybe clamps and bolts, when changing lifters.