It's both, with the external gate inside there (and inverted) to hide it from the prying eyes of the public it was impossible to put an adequatly sized Cat in the stock locale.

Actually scratch that, the stock cat would fit with the right endtank -just wouldnt have the WG flow coming thru it.

I have a few monolith's in mind that will physically fit and be adequate in Mass to not turn into a platinum/ceramic mess after 4 or 5 full throttle blasts (your doubling the heat input with all this "extra" power).

If sufficient demand exists, I will proceed with the engieering of a correctly sized and performance oriented Catalyst. It will be then offered to kit owners that require it at an very inexpensive rate.

All exhuasts that will bolt up to the stock cat flange will work fine. All mods after the factory compressor discharge elbow will work fine. (intercoolers,piping from Hahn or Double D should fit no prob).
But other manufacturer's downpipe or highflow cat's wont directly bolt on here. The position of the turbine shaft is lower and spread more twards the pass side of the vehicle to fit that honkin' GT30 in there.