UPDATE!

Bentusi123, I change the flex pipe today (again), this time to a larger flex pipe and the sounds pretty much disappeared! The response is pretty good down low. I would imagine it will improve over the next few weeks after the ecu adapts to the change.
Since u are in Sydney as well, there are a few good exhaust shops u can get the flexi replaced. I highly recommend the one i went to in northmead called Performance Exhaust. Great service and they do a superb job! Let them know Wes recommended u so maybe they can do a better deal for u.
Get the flexi changed and u should be pretty happy