low down torque & power

[GXR]

Hi all. My name is Geoff & I am a new member & this is my first time online. My brother, Roy, & I were at our first club meeting at the Dingley International. What a great night. I look forward to attending many more meetings & events & meeting many members in the future.

Anyway, I have just purchased an AU XR6 VCT series 3 Falcon (manual) & want to increase low end torque & power with consideration of $$$$ spent to a minimum.
I want to fit an airbox (I believe about 12 - 15 rwkw gain), in addition to the following.

QUESTIONS:
1. I have read on Ford Forums the VCT engine just needs an Airbox & high
flow Cat converter. The rest of the exhaust is OK. Is this true?
(After the Cat converter my exhaust is twin then back to single after the
diff.)

2. As well as the Airbox, should I fit:
(A) Extractors only?
(B) Extractors & high flow Cat converter?
(C) Extractors, high flow Cat converter & Cat back exhaust?

The entire exhaust system on the car is in excellent condition. I want to keep the car looking & if possible sounding stock standard from the outside.

What power & torque gains would I expect from options A, B & C? I would like to have actual dyno figures to support this not just hear say.

Any help would be greatly appreciated.