hey mate
on knocin out the honeycomb shit in ya cat i done this a while a go and didnt notice any difference BUT if ya gona get a cat back exsaust as wel ya neva know!!!
it could be worth a shot but if ya got a little bit of coin it might be worth goin the lot i got my extractors hi flow cat and exsaust for under $1000 but i wouldin say it was out of the best materials eather
let us know how you go with it all??
If I was you I wouldn't knock the honeycomb shit out of your cat. I have been told it is up to a $25000 fine. Sure it makes car go better but is it worth a fine potentially that big, think of it as about 10 times the value of a pintara. I beleive a high flow cat is only beneficial to highly tuned engines or engines that have a larger capacity that 2.4ltr.
When a car blows the exhaust gases out from the engine they a swirling, in a standard cat the honeycomb brick has hundreds of little squares the gases have to find their way through, in a hi flow cat the mesh stuff is in a swirly pattern therefore making it easier for the gases to flow through hence the name hi flow cat.
If you want to upgrade the cat Noss (I think) did a write up which is probably in the wiki section now, on installing a cat from a magna, I think it was a tj model. They are a bigger cat, flow better (obviously because they are on a bigger engine) and can be got from the wreckers for about $80-$100. Just check that you can see through cat, if you can it is good.
Just my 2 cents worth.
Edit: It is also a defect from the rta for pollutuion and excess noise (have to check this one).
I had a mate who has a substantially modified nissan exa wich had no cat and he was defected for pollution and excess noise.
Edit #2: Here is the link for the magna cat 'conversion':
http://www.antrx.com/smf/index.php?topic=4503