Im just bout to install a set of pacies and am wondering if there Is there much point in getting a high flow cat in my I6 AU's exhaust system?......because ive heard that the stock cats flow plenty.....wot kind of gains would i expect?....aparantly not much at all(1kw if that) is wot ive heard. I already have cat back exhaust system. So any help would be apreciated..........

while your doing the system get the high flow cat, the standard cat isent restrictive at standard performance, once you start bumping up your performance, a high flow cat starts to become recommended and frees up more power. im getting a full system on my BA soon and a high flow 100cpi cat is about 130 bucks ontop of the cost of headers and catback, including fitment. now 100cpi cat is illegal but so is ANY modification to the standard cat which i believe is 400cpi so really 100cpi is only slightly more illegal then a 200cpi

Standard cat on AU is pretty good but when i had mine changed to hi flow i saw the actual size difference between the standard cat vs 63mm and it was fairly noticeable. I had the whole system done at the same time so couldn't tell ya the actual difference it'd make going from yours. (except the price, which was $367 retail this year but i got it for $150 ).

But like winman says you might as well put it in if you're going to do other mods and if your budget can stretch. Also agree with uniacidz - it might need replacing anyway.