For $50, you can't complain. A full rebuild of it would only run around $300 worst case, and that would only be needed if it were in bad shape. And a little side play is fine, but in/out is bad...
If its from Hahn, its probably one of their strange 'Super' 20g's, which are a Mitsu 10cm housing, mated to a td05 compressor. I can't remember if they clip or not, but I am pretty sure they don't.
On a 4g63, with proper plumbing(IC, Exhaust, etc), stock everything else, that should be at full spool around 3500 rpm. On the KA, I'd expect around 3200, unless you have some head port work on the exhaust side. One thing I will say is that the 20g isn't really efficient until it hits 18+ psi.
You'll find that many DSMers consider the 10cm housing to be undesirable, causing too much lag, for minimal top end gains. A better solution for the 20g is a 7cm housing and a 10-15 degree clip(this, I believe is what Buschur sells, I'll ask next time I am talking to him) It results in better spool, about the same top end power, but a fatter powerband. Again, the turbo really shines after 18psi.
http://turbochargers.com/Turbo...5.htmIs that what you have, or is the inlet on the exhaust housing larger?