Refueling would solve so many problems. Two, three or four stints where cars are driving flat out rather than circulating to manage fuel, tyres, engines and gearboxes.
What are you using to measure HC?
The stock ecu will run pig rich with higher boost/more airflow. Sure in closed loop it will trim when cruising but there is no doubt that aftermarket engine management wakes these cars up and improves fuel economy compared to the factory ecu once you start modifying them.
Who won't return your email?
ps. I would be taking it easy on that new turbo until you get the Nistune installed and tuned and it is easy enough to remove the front driveshaft and use a 2WD dyno.
Usually it will be an issue under load when it comes to coils.
However I had the same issue when the RS4S arrived from Japan. There was an intermittent check light.
Consult was indicating a CAS issue but it was checked and was fine. At some point when the coils were replaced the issue resolved.
There are some cheap fixes for coils such as spraying them with urethane seal coat (CRC product) and checking the plugs/wiring to the coils. It might not be the issue but it is worth trying the cheap options like this as a starting point.
A quick search would have found this thread from last week. Yes they are well made, they are $250 delivered for a 5" body cat with flanges.
http://www.skylinesaustralia.com/forums/topic/367875-what-cat-should-i-get/page__view__findpost__p__5867645
Scan would be good. A mate wants to come but it is dependent which weekend due to custody of his kids being alternate weekends. Hopefully it is the last weekend including Sunday 1 April.
Well there is your answer from AVO if they think it is a cam gear issue.
Talk to one of the other shops, show them the dyno charts and see what they say.