does anyone know if the HKS replica y pipe works with a tomei cat back system

 

HKS are TD, no Y-pipe.

 

https://www.z1motorsports.com/exhaus...e-p-10982.html

If you're referring to the knock off of this HKS Y-pipe, you should not have any issues with the Tomei exhaust. The Tomei was designed to fit with the stock one so this should line up the same. Just keep in mind that replica parts in general do not fit well to begin with.