I'm breaking in a motor so I'm not boosting or going over 3k.
The noise sounds like the exhaust is rattling but it's not I checked that.
Sounds like metal to metal noise fluttering quickly.

I have my BOV vented to atmosphere due to TID mod for to4 upgraded turbo.

During decelaration (goes away with any throttle) I here the noise.

It happens only when the car is fully warmed up.

What are noises that only occur during decelaration?

 

Maybe its your turbo heat sheild?

Also are you sure it is only on decel? Maybe it happens during accel but you cant hear it over your engine. Just a thought.

 

No it's only during decel.
I have had the hood up and listened while pulling the throttle cable by hand.

I dont think it's the heat shield.
I put my ear to the precat from under the car and I can feel it and hear it.

 

Does it when I shut the car off also.

 

I dont know what else it could be. I get a rattle when I shut off my car too but thats because I couldnt take the heatshield totally off.

 

Maybe it is the heat shield.

BTW why did you take the heat shield off?

 

maybe an exhaust hangers weld broke, and it normally will rattle in decelleration

 

yeah might be it does sound like exhaust rattling

The shop I used to work for has kevlar gloves I can use to grab exhaust and see if the noise changes.

 

I had a rattle/buzz when that metal bulge thingy on my air return line was vibrating against the heat shield right beside the downpipe. Only happened at idle. Use some wire to hold the air return line a little further away from the shield and see whatcha get.

 

I'll try that.
Are you talking about the line that goes to the cat?

 

I had to take off the heat shield to install my downpipe. Most people say that theres were already rusted to hell and broke apart. Mine was in pretty good condition but I could not for the life of me get it off. I just took of the screws and spread it apart to do the job and pushed it back together. I couldnt reattach it with the screws since the head of the screw broke off due to rust.

 

Correct-a-mundo!

 

one other thing, any exhaust heat shields could be rattling, mine does all the time

 

I have the exact same thing happen to my 91 n/a...but it has never occured in my T2...

I use the n/a as the daily driver and two weeks ago it started...just like you said...a fluttering noise under decel. Hopefully this weekend I can put it up on the lift and check out the exhaust...its definately annoying though! lol

 

Thanks for all the info .

The wierd thing is it only does it once the car is warm never when I first start the car up.

 

umm, then it's prolly a heat shield somewhere

 

Do heat shields normally only rattle when hot if they rattle?

 

I dont know exactly, but my exhaust manifold heat shield rattles because it bounces against the manifold, maybe you should start it an let it sit, and then look under the hood at the exhaust manifold heat shield, and that could be the problem

 

I installed my blitz bov and now I can see when my bov is open.

It only does the noise when the bov is open.
I think it is a small backfire or something from the open bov.

Maybe I need to adjust the spring because it opens easy in neutral under very light throttle.

Should it open that easy?