HHT : Toning down noisy data
As a pragmatic applied mathematician who has job to do, say, rather than to prove something via theorem or induction, my first approach would be to reconstruct the time series without IMF C2 and C3 and see what happens. I think that's the equivalent of using noise filters in the FFT or deleting outliers in a data set.

As an aside, I'm impressed that you could pick up and utilize the HHT so quickly. Kudos to you.