I have a 06 5at coupe, only mods are plenum spacer and ztube. It makes a weird whistling sound everything I start her up. In the video I started her up a couple of times and each time you are able to hear it. Any help will be greatly appreaciated.

 

Sounds like a weak BOV lol, I'd pop the hood and have a buddy start her up while you try and pinpoint whether it's coming from your intake manifold or ztube.

 

check make sure the manifold is completely sealed with nothing stuck in between it ie oil filler "guard"

 

I havent been able to make out what is making the noise. I am also getting some rattling. Can it be a bad cat? back in september I had the passenger cat replace because the inside had came loose and was rattling. I was not getting any check engine light back when that was happening, and I do not have a check light on this time either.

 

Anybody ever had this problem before?