So there is no way to have vta on a EVO. Without messing with maf?
VTA is fine, don't listen to those people.
What spring are you running now? I have the same thing, Tial 50mm VTA. You'll want a -9psi spring. -12 is way too stiff and the valve won't even open at full boost...you'll get some crazy off throttle surge.
You're getting a little surge (fluttering) because the BOV is staying closed, like it's supposed to, and your turbo is basically spooling too fast at part throttle, flowing more air than the engine can take in. Either adjust your right foot, or adjust your MIVEC and wastegate duty cycles a little so it doesn't spool so fast at part throttle.
There will always be part throttle situations with high load/low rpm when you can't avoid that light surge, but you can minimize it by tweaking the above mentioned tables.