Seems like the feedback on tt.net is about 50/50 on these being installed correctly (no whine) from various shops around the US. I'd almost be willing to suck it up and ship it out to Greg Dupree's shop of choice. If you are looking local, I'd also consider some of the well respected domestic shops in VA as I'd bet the domestic guys swap out gears a lot more often than your average import "tuner" shop (just a guess though) and I doubt swapping gears in the Z diff is that much different than a lot of other cars. My dad has a shop in mind for his leader gear install (and Quaife LSD); I'll check who he is using.

Also, are your gears from the first Leader run, or one of the later batches?