Which widget are we looking at Barney, the one on the far right of this photo?
I *think* that's the exhaust gas recirculation controller, it holds the valve open that allows exhaust gas to recirculate back into the intake manifold on overrun and/or idle. However if it sticks, it leaves the EGR valve open under boost and all your boost pressure vents into the exhaust manifold...
My physical valve stuck on mine and the car felt really sluggish, if you've disconnected the hose and it's running better it may be your electrical valve is shot...