I have a Fg mk 2 xr6 with extractors, 2.5 inch system and
Ss inductions growler cold air induction. It still has the factory cat, is it worth
Getting a hi flow cat? Or will the performance and better sound be minimal
Thanks in advance.

I am sure it would help to get a better cat, just make sure it is a minimum of 200 CPSI (Cell per Square Inch) and stell inner, NOT ceramic. I was told that using the 100 CPSI was not legal.

There is this one https://www.ebay.com.au/itm/MRC-VENOM-H ... SwUYNaApvj
It IS 3" diameter though? I am sure they would have 2.5 inch.

Like this one, it is 2.5"
https://www.ebay.com.au/itm/MRC-VENOM-h ... SwAC1Z~7Cl