we sold a set of HSDs to a customer who dropped his lap time on the QR sprint circuit by nearly 2 seconds after getting them installed and enabling the car to be better corner balanced.
I'd be thinking you have a boost leak somewhere. best way to test is to remove the AFM and feed compressed air into the intake, but you need a special bung and tyre valve contraption to test it that way.
a bit of a nuisance, you can get a new barrel but it most likely wont match your existing key. you will probably have to get a barrel and key combination, you should be able to get 2nd hand from an import wrecker.
does the car heat up quickly or does it only get hot say after a decent run on the freeway? it its the latter then there could be a blockage in the radiator which can be fixed by a radiator specialist.
can you list EVERYTHING you have tried so far, so we are not suggesting something you have already tried?
I know you have said you have replaced every sensor, but "every" doesnt always mean "every".
the road to Morgan Park:
1. Join the Z Car Club of Qld, contact me and I will put you on to Dave Robertson on how to do so.
2. He should be able to get you organised for entry in next year's series at MP.