Is it water cooled?

The water primarily cools it and the oil also cools. If it is not water cooled then you ONLY the oil will be cooling it. You could slightly increase the size of your restrictor if you think it will help.

But remember, this turbo is mounted FAR away from the exhaust manifold and less likely to run as hot as it would right off the manifold.
The turbo may have been basically fine, but those hot spots could have developed before hand since it was used and not rebuilt. What kind of car was it run on before?

Former owner of '99 CSVT - Silver #222/2760 356/334 wHP/TQ at 10psi on pump gas! See My Mods '05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red '06 Mazda5 Touring, 5spd,MTX, Black