[jay-craven]

It's the lever/rod attached to the turbo and actuator. What it does is control boost, If it's not shuting correctly due to soot/oil or the actuator is faulty you will be getting delays with the turbo.
The egr is the system of pipes that run from the exhaust to the inlet manifold. Lots of black smoke/soot are associated with egr but could also cake the turbo with crap causing the boost delays.
Just an idea mate.