Exhaust Deceleration Noise

2001 Porsche Boxster S, manual 6 speed. 45k miles. Only modification is the following exhaust. I recently completed some exhaust work. Removed the secondary Cats and replaced the muffler with a Circuit Works V2. Right after this modification I have very noticeable noise in the exhaust while decelerating. I notice it from 3500 RPM's down to 1400 RPM's. It may be doing this above 3500 but too many other noises going on. It does not do it at all cold. While cold and only for maybe a minute it does not make this noise while decelerating. After it starts to warm up the decal noise starts. It does stop making this noise as it comes down through the rev range at 1400 RPM down to idle.
I have used chassis ears to listen to all mechanical hard parts and it is not coming from the engine internals or the cylinder heads. It is not coming from a rattle in the manifold cats. Coming straight out of the tail pipe. Sounds to me like an a air or air valve, air solenoid sound.
I found other posts about this issue some going back over 10 years. But all posts about this I could find did not have a resolution or even any suggestions about how to correct this deceleration noise. I have attached 3 links to YouTube videos from other Boxster Owners with the same exact sound.

[www.youtube.com]
[www.youtube.com]
[www.youtube.com]

Could be a loose baffle inside the muffler can.
Try hitting it with a rubber mallet checking for the rattle.

Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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On Wolfi, I used to get metallic rattles on deceleration. Cause was easy to determine though by looking underneath the car @ the rear. The steel mesh heat shields around the bottom of the stock Porsche catalytic converters (2) were rusted. I simply removed the rusted mesh w/tin snips & noise went away.

JB/SE SoDak
1997 986 - Wolfi
Yankton, SD

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No rattles anywhere in the exhaust system. I've used chassis ears to listen directly to the muffler and all exhaust components while it's making the sound. Not a single noise from the pipes, manifolds or muffler. The sound comes out of the exhaust pipes. It sounds like air from an air pump, like an air compressor without the loud motor. Could this have something to do with the secondary air pump system?