I was concerned about the balance myself, but what that other guy said, he made it sound like it wasn't an absolute have to thing.
The other thing, I'd have to ship mine, because there's no-one close that has the tooling that can balance these things.
He also said that they do quite a few impeller replacements, and alot of people opt out of having the Garretts (GTP38, TP38)balanced due to the cost, and they've not ever had one come back with damage, or excessive wear due to being out of balance , but on the other hand...they recommend balancing the Holset......so...dunno...
I dunno though.....120,??? rpms is awful fast to be out of balance, even if it's only a few grams
did they state why they feel the need to balance holset turbochargers?
are you simply rebuilding it or are you planning a wheel upgrade as well?