up the power

Bigfish

G'day i live in brisbane and have just picked my Z up from the dealer last week. i have beein callin around tryin to find someone that will do up grades on the ecu and the likes and so far only one has come back to me with any help and it was to replace the factory unit with a haltech but im not sure i want to replace the hole ecu. it seams that there is no one in the area that has worked on these car as yet, has anyone had any work done or does nissan do any factory upgrades.
the other thing is has anyone done a full headers back system yet and how did u get around the O2 sencer warning lights.

thanks,
bigfish