there are different types of fluttering... under full boost the ewg should be fully open, no fluttering just pure woosh.. the boost should hit hard too, no fluttering. when getting on and off the gas some times it flutters trying to slap open and closed but def not under daily driving conditions. if your running a 3 port ebc you def need to make sure its hooked up right. i run a old school mbc so there is never any guess work, but im old school, so i dont know about the fan dangled new cars and how they act.
here is a little cruise i did and you can here the ewg opening smoothly... the fluttering is my over tightened tial bov... because race car.