'Sooting' on my Saab ttid

[Stevepritch]

I am getting a blackish deposit on the back of my car. Changed the ERG 2 months ago and it ran ok for a while. Started shooting again and engine warning 'Limited Performance's comes up. It will also clear if the engine can be ran at 3.5k revs for a while, big cloud of black when it clears. Did have an economy remap which hold off turbos until 50% of accelerator used and boosted turn pressure to 22psi.
Any assistance welcomed.