GCMS Peak Identification: Online or Open Source / Free Programs?
Have you tried the Golm Metabolome Database?
It is a collection of GCMS mass spectra. The focus is on metabolites.

However, on their webpage is the entry "Decision Trees". If you follow the link, there is the option to enter your own mass spectra information and receive a prediction of functional groups in the measured substance.
This might be of help to identify your molecule.
There are more details in the Wikipedia entry.