Using HP filter to filter Dynare's output


I would like to apply a one-sided HP filter to the data, generated by Dynare (stoch_simul, order=2 or 3).
To obtain Dynare’s data, is it sufficient to add steady state values (oo_.steadystate) to the deviations from steady state (oo_.irfs.*)?

Would appreciate your comments.

You are not supposed to filter IRFs. You should set periods=x and then filter oo_.endo_simul or the variables saved in the workspace.