Re:
Carbon? What's that?
But seriously, if it's a critical part like a seatpost or stem, you'd probably be best off taking it to a good bike shop you trust to have a look, or even sending it back to the manufacturer. At the very least, go over the part with a magnifying glass to look for any cracks.
If it didn't actually crack or creak or anything, maybe you'd be ok, but personally I don't trust carbon much and I'd be cautious.
Ritchey and Bontrager do torque keys that are pre-set to 5nm. Handy to take along if you're test riding a new bike and want to fillw with seatpost height and so on.
