You could remove the compressor cover with turbo installed and measure the side to side movement. Gotta be careful removing and re-installing comp cover to be sure you don't damage the impeller but it's not witchcraft.
You could measure radial movement with a dial indicator attached to a magnetic base (stick it to bearing housing), or with dial calipers measuring the gap between wheel and bearing hsg, or maybe use feeler guages in the gap. Measurements are "total" movement...ie pull the impeller in one direction and measure gap or set dial indicator to zero...then push impeller 180 degrees in other direction and measure new gap or read dial indicator. Max gap minus min gap is the radial movement that shouldn't be more than .021"
While omp cover is removed examine carefully for contact with impeller....any rubbing and there is too much radial shaft play.
lol. wow that is rocket science. Its not rubbing. Can we just be safe to safe if it not touching then its ok. What kind of power loss do you think you would exspect is it was more than .021 side to side?
Side to side radial play has nothing to do with power or power loss. But it will increase exponentially as the bearings and shaft wear. It's all about 100k+ rpm aluminum piece rubbing on another aluminum piece...just a little bit and blammo.