That sounds more like an air leak than a ruined turbo. I really cant see why all of a sudden the oil seals on the turbo would blow after you changed a DV that was nowhere near the turbo. You should check for boost leaks, hoses, clamps, tears in pipes, intercooler pipes. The whole boost system, probably easiest to get a garage to do a smoke test.
How does it feel to drive? still getting the kick up the arse at 2500rpm?
