Love the new Greddy FV. Swapped this one with my aging Type-S, went re-circulating route and install was only about 5 minutes. Immediately noticed turbo flutter from 2-3psi or less even with the softest adjustments. Popped it back off and did the single spring mod most people do with their Type-S'. Reinstalled and she's running like a champ, holding full boost @ 21psi with no lift, and only the slightest flutter in 5th gear with low pressure changes. All in all it was only about 30 minutes of work with just a little more tuning required. Definitely a lot quieter than the Type-S but makes a real nice whooshing sound. Hope this helps.
Single Spring Mod: http://www.evomoto.com/tech_info.php?tech_id=7
I went with the single large spring with around 2 full turns from first contact with the spring perch.