High flow cats are just a sales pitch.. I have done research and asked so many exhaust shops and they all say the same thing, there is no real high flow and just more money for the name. One thing is if you start messing around with the cat with no codes showing up ,the o2 sensor and new cat may be out and throw codes.
I was considering the same on my 3.0 but my a mechanic friend told me it not worth it and to possibly have the ecu throw codes
The "high flow" CATs are either metal spun or semi-hollow for flow but looks like a CAT.
The metal CATs replaced the ceramic since they heat up quicker and allow for a little less back pressure, not much, because a clean CAT flows easily anyway.
The companies that sell the "hollow" CAT advertise not for on road use. Its just a "cat" for auto-x or other sanctioned racing that requires a CAT to be installed to qualify.
Unless you are increasing the output of the engine with a turbo that raises the VE, then a stock style CAT is all that's needed if the OE ever needs replacement. If it does ever need replacing, you will need to find out what killed it or the new one will die early also.