How small a peak could one identify by GCMS I'm trying to characterize the impurity profile of an organic liquid sample that is already described as 99.7% pure (Boiling Point 230 C). 

Would a GC-MS be a viable way to identify the smaller peaks? e.g. How small a peak could one expect to get a decent mass spec. pattern for? Say, a peak with 0.01%  of total peak area, would it be viable to identify it on a GC-MS?

I'm assuming the smaller peaks can be resolved satisfactorily. I don't need quantification of the peaks just identification. I can match against the NIST library of spectra but also have a clue based on the manufacturing process about what the likely impurities may be.
You can get GCMS peaks for very small components of the overall mixture.  

However, most GCMS patterns are electron impact, and hence probabilistic, so if you don't have enough sample, the fingerprint won't be reliable.

In my experience 0.3% produces spectra which are 'good enough'... as long as you don't inadvertently overload your column.