that's the thing, you'll need a complete "kit"
even with all the turbo parts in place; you'll still need electronic control. Your ECU isn't programmed to suit a turbo.
Perform a search on the MR2 board (
http://www.board.mr2faq.com )
or just look throughout their archives. You'll see plenty of info on how to turbo a 5S-FE.
I'm no expert in turbocharging , normally NA engines. So, I can only point you in some direction.
Good Luck