I just replaced my wear ring. It was the original factory ring with 40 hours on it. The clearance was about .020" or less all the way around. It also had two grooves worn into it where a rock got stuck in the impeller. The new wear ring has between 0.00" and 0.005" clearance. I had to turn the impeller by hand to make it "machine" the ring in some spots -- nice and tight.

Now here the interesting part. With the old worn wear ring, the rpms would jump right to 7500-7600 and then pull to 8050 at top speed. With the new wear ring, the rpms jump to 7200 and then pull to 8050 at top speed, which makes sense since with the tighter clearance, there should be less slip initially.

But, it seems like it pulled harder with the worn out wear ring. Maybe since the rpm would jump up higher, I was into more boost earlier and it would actually pull harder kinda' like a stall converter on a drag car? I dunno. Green wheel is going in next so I should be making more boost down low which should help.