Berks High Flow Cats

[willyz30]

I have an 09 G37 XS Sedan. The vehicle is stock except for the cats and a Stillen underdrive pulley. One of the stock cats had begun rattling so I replaced the stock catalytic converters with a set from Berks. Everything sounds fine when idling or driving normal, but there is a serious rasp when accelerating hard, especially in 1st and 2nd gear. It doesn't sound good, almost like a high pitched in can like rattle. I took it back to the exhaust shop and it was determined the sounds was coming from the area after the cats where the exhaust goes from 2 pipes to one. (joint of the Y pipe). I was told that the noise is excess air being bottled up at a choke point. Nothing was loose and no leaked were noticed. Has anyone else experienced this? Will getting better flowing pipes resolve this?

Thanks

[willyz30]

Sorry typo, I meant "tin can".

[willyz30]

I had bigger exhaust pipes put on and eliminated the Y pipe.
https://www.youtube.com/watch?v=k3rKZLNnSAk

[RED_DET]

Rasp and hissing sounds are normal with some HFC's. Nature of the beast.

[willyz30]

https://www.youtube.com/watch?v=AyWs0I9 ... e=youtu.be