So you haven't bought this car yet, but you have ready access to it to see whats wrong with it?
GTR 4WD LIGHT THREAD
For $17k it can't look that good under the bonnet, like psybic says the paint on the plenum is probably all cracked and peeling . Ask the current owner if you can take it for a compression test, its $xxx money well spent on a car thats more than likely ready for a rebuild.