I currently have the vibrant header and downpipe combo with GM performance cat back out the back. I am wondering if the OEM downpipe will bolt up in between the header and cat back.

 

No... it will not.

 

It would bolt to the exhaust but not the header. I have an extra stock header if you need one

 

Does anyone know what the fitment issue would be? Im trying to sell and need to smog

 

ummm.... the fitment issue is the stock downpipe was designed for the stock manifold not a midlength style header. The connection flanges are totally different as are the lengths.

you would need a stock manifold or shorty header to run the factory downpipe. sorry.