Hello in rebut to the remark your regulator needs to be detuned. That is an incorrect statement. There are three reasons why a regulator will shudder:
1. The second stage has been set to be too sensitive, therefore creating a turbulent action within the second stage body.
2. The second stage has been set to rigid, where there is a need to inhale too deeply or quickly to overcome cracking pressure, thus also creating a turbulent action within the second stage body.
3. The incorrect repairs of the 1st and second stage reg. this tends to be more likely the reason. The hp and lp seat from some manufacturers has 2 sides one side is for use the other has a slight depression in the center, those seats are just turned around to use the other side (which was not intended to be used) the depression in the center of the seat will cause cavitation and turbulence in both the 1st and second stage, therefore a shuddering sensation to the diver upon each inhalation. With the exception of the Dacor extreme second stage (which had some design flaws which consistently showed breathing simulations of shuddering, those problems have been corrected by Dacor and that model should not have problems like that any more) But getting back to the initial problem there is not a regulator manufactured today that has shuddering problems in the second stage after the proper repairs and setting to manufacturers spec's.
As far as giving anyone that is not a qualified regulator repair technician advice on doing repairs to their own equipment, which is (life support equipment) I would not recommend it because "you" will assume the liability if that advice is followed. And it is also against the policies of the manufacturers.