I'll tell you what. Latest MHD update was quite weird but I don't think it has anything to do with the flutter. In adaptations, I would reset load and lambda for MHD.
For the fluttering noise, I think you may have the same problem as me which is a compressor surge. The sound is produced by the DV but it comes out of the intake. I'll link my video showing how mine sounds. Basically your stock DV is broken. I am remplacing my DV with a DV+ from GFB.
But if you are not running stock DV or logs show weird things with boost then it might not necessarily be a compressor surge.