Had a talk with the guy who owns Hitech mufflers in Sydney yesterday and he reckons changing the exhaust from cat back will yield a 10% increase in the low-mid range!He did a cat back system for the guy that manages Snap-on tools(06 Euro)and offered to do mine for $1600.if i'm not happy with it he'll take it off and give me my money back!!!www.hitechmufflers.com.au