I just recently got a new clutch installed, however i was going to purchase a PBR clutch kit and the place who installed mine adviced not to. They said nothing 'bad' about PBR but they gave me a very confused look when i requested a PBR kit (my uncle told me they were good, though he works with holdens and fords).. so i asked what was wrong with PBR clutchs and they said they prefer excede because they deal 'more' with high performance cars.
So my suggestion is the clutch is probably not suited and doesn't have a large enough pressure plate to cope with the power of your stockish r33 gtst. Go to another place and ask them what they think it is, and as someone else said, ask them for an explaination as to whats wrong with it, as they should have test drove it, if they cannot give it.. ask for a refund on all labour.
Goodluck mate
Dayne