Correct me if im wrong but I dont think turbo flutter is something you should strive for. Its ok to have a little under extreme situations but its in general not a healthy thing for the turbo.
To the question about which aftermarket DV/BOV allow adjustment. Suppose it a big rigged to get it that way but he's using a GFB response valve (is this the same as the DVX?) and making a slight adjustment/mod to be able to get some flutter (adj to block off the recirc side and then set to recric) vs. discharge to atm: