unless you get a piggy back system like Xede/Unichip there is no point buying a chip with a stock car as when you put on an exhaust or extractors etc you will have to send the chip back and get it re-programed $$$$$$$$ costs more in the long run.
Do the usual extractors, exhaust, larger intake snorkle, k&n filter or similar), then get a chip, as it can be programed to suit your modifications.
I did all the above and a 3.45 diff ratio change on a ebxr6 i had some 10 years ago. I got a chip torque chip and pulled a flat 15.01. From memory i got the "hp3" chip, as i said this was 10 years ago so give them a ring. Or look at thier website www.chiptorque.com.au
The diff change made a big difference and so did the chip.
Hope this helps