buying a used set up

Won't work if you don't have a carb setup for blowthrough!!

Do it yourself! Not real hard but the tuning could be a nightmare if your looking for big hp.

Here is a link,
http://www.hangar18fabrication.com/blowthru.html

As far as a used turbo, make sure there is no shaft play (in/out up/down) whatsoever! Look hard at the inside of the exhaust housing for signs of oil discharge. Last but not least check the compressor and turbine wheels for any damage. Even a nick will cause you big problems.