Only reason I would see the standard suspension not passing the test would be that the shocks are all worn out or the whole system is in really bad condition. With GTR's being ~18 years old, I'd imagine finding a set of good condition shocks will be very difficult.
Wouldn't have a clue about the white or silver thing. Can't think of anything that it would relate to.
One way if seeing if the shocks are in 'good enough' condition is push them down and if they travel back to its position slowly, they should be fine and if they go straight back to their original position in say 1 sec (or quick), then they could be f**ked. Don't know if my way of testing is good, but it should give you an idea of what condition the shocks are in.
Edit: $250 is a bit pricey for a set of second hands. I purchased a set for $150 and they were in good-ish condition.