How much Head modifications if any will a standard AU ECU take?

Its a AU fairmont with Hurrican Xtractors, Mandrel Bent Exhaust 2.5", SS Induction, currently installing Stage 3 Crow cram, an custom Chip Talk Chip.

thanks

As much as you like.

Working an I6 head will not cause any dramas with the ecu.

porting and chamber work with up to AU or EF-EL XR6 size valves will work well with a std ecu.

The gains to be made with the head at high revs can't be realised with the std cam though and the cam overlap and duration will play havoc with the std ecu hence the chiptorque chip with the crow stg 3 cams to allow it to idle!