So I recieved a "mint condition" turbo from the miata.net classifieds, and now have noticed that it has three tiny cracks in the hole the internal wastegate gasses flow through. This seems like a problem but I thought I heard somewhere that it is normal.

Hairline cracks commonly develop. I'm sure you can get a replacement turbine housing on the cheap if you want to replace it. My "mint" kit from m.net was anything but mint.

So I've been looking for a replacement, but the one I found might be a little overkill. What do you guys think? http://cgi.ebay.com/ebaymotors/T3-T4...06703646QQrdZ1

I was thinking more on the lines of this:

http://www.turboneticsinc.com/pa_turbhous.htm

Well the turbo also has some side to side play, so I was thinking on just replacing it.

Save yourself the trouble of having to take it off right after to put it on and just have it rebuilt. I thought turbonetics was reasonable. I won't buy a used turbo again, my experiences have also been bad. I wouldn't worry too much about the hairline cracks, I have reinstalled a turbo with significant cracks and it lasted for a long time with plenty of boost and only failed when the seals went.

Yeah used turbos are a bad idea, the excellent condition used turbo does not exist.