Changing the turbine housing may very well fix it. Before installing the turbine housing they spin the wheel at high speed on a machine to test the bearings and balance. That's why I mentioned exhaust housing/wheel clearance a few posts back. Did you ever try to spin it by hand with the turbine housing removed and see if it spun better than when its installed? On my new turbo's for the twin setup I removed the turbine housings for coating and then mounted them to feed pipes that way since it was easier to get to the 4 stud bolts. The wheels spun fine by hand on both turbos, when I installed one into the turbine housing again it seized and wouldn't spin. I tried as hard as I could to spin the wheel with both hands and it wouldn't budge. I was beside myself for awhile couldn't figure it out. Then decided to swap and put the other turbo in, bolted the turbine housing down and it spun no problem just as easy as it did when the turbine was out. Put the one that was seizing in the other turbine housing and it was good to go, spun no problem. So the wheel is cut installed in the center section with the bearings and then spun at high speed, then material is trimmed/removed around the center bolt to balance it. Then the cast turbine housing is installed on the wheel and bolted to the center section. If there is an imperfection in the casting it can slow down the wheel or seize it, like what happened to me. Then the center is packed with grease before the turbo is inspected and sent out, that grease packing makes it very hard to spin initialy by hand so if the turbine housing was impeding the wheel it may not have been caught on a freshly assembled turbo. Their new machine allows them to spin the turbo and allow the grease to spread out and break it in prior to shipping now, so no 500-1000 mile break in is not required anymore on the oil-less units.