OK, from the top...
The restriction was adjustable (ball valve) and has definately been removed... Good idea thought...
Firstly, you are correct... This has nothing to do with the controling system... The front half of the exhaust is about as good as it's going to get ATM... I still haven't had a chance to drop the cat back and take it for a spin to see how that goes... I understand what your saying about the wastegate outlet and I've heard of this being done before... But as Doctor says below, it's not a common problem... I'm honestly not confident enough myself to go filing / grinding away at the exhaust housing of my turbo... If it comes to that, I'll send it to GCG and they can "go to town" on it...
Doctor, when I wired the gate open, I did remove the actuator arm from the gate flap... The flap was, as you say, flapping... I then wired the flap open so there was no chance of it flapping closed when I was testing it... I hope you understand what I'm saying... There was no tension / preload on the wastegate flap at all... It was 100% open for 100% of the time I tested it...
With this setup, it still made excessive boost...
So I don't think it's the control arm as this was disconnected...
As you say though, it's probably something really simple... I just can't for the life of me work it out...
Thanks all...