Bit of progress today.
A couple of days ago I re-flashed the ECU. Just with the stock values, but with the throttle restriction removed, Speed limited to 300km/h, and a little adjustment of the rev limit/fuel cut/ throttle cut. All went successfully.
I have been having a problem with the ECU learning some strange fuel settings on closed loop. Basically what was happening was that on closed loop, Bank 2 was running a lot richer than Bank 1. it was about 80%/120% ratio. It didn't occur when the ECU was just fresh, but when it had driven for ~150kms, and the ECU learnt it. At the time it was stock ecu, not re-flashed at all. When it went open loop, it was fine. It spat a U1000 error, which is CAN bus error. Now nothing is wrong with the CAN bus, but what triggers that code, is when the ECU doesn't receive data from the emissions diagnostics for more than 2 seconds. So I went searching today- first port of call the bank 2 wideband sensor. When I pulled it apart it seemed ok, but the little rubber thingo in there wasn't sitting quite right so I pushed it all the way to the bottom, cleaned the plugs out and reconnected it. Also found a nipple in the intake tubes wasn't tight, so tightened that up. Anyways, the problem is absent now, I haven't put that many kms on it yet since the last "clear learned fuel" but I am optimistic that it will stay away. Idle is nice and smooth now, and while there is a little inconsistency,its not much, and doesn't appear when the car is at cruise with light throttle.
I want to know that the problem is gone, before I proceed with 600cc Injectors and fuel pump and tuning, as that would just exasperate the issue.
Also wired up my boost gauge, so now I know wtf is going on at night too!