Car won't rev out properly
 

hey guys i have an evo 8 and need a bit of help cant figure it out. when it gets to about 5k revs it starts whistling heaps loud and losses power so after checking for boost leaks and not being able to figure it out we took the ****ty air filter out and it revved out perfectly. I bought a k&n drop in panel filter but still wants to start doing it around 6k now anyone had a problem like this or could offer some advice would be much appreciated. thinking i need a new intake maybe?

Did you actually pressurize the system to test for the boost leak, or did you just fiddle with the clamps and vacuum lines?

was taken to a shop where they pressurized it and couldnt find a leak anywhere

BV perhaps?