Originally Posted by
saphcosmike
penny ?? you mean the wastegate itself ??
I thought actuator straight away as he has wound the boost up a bit a few weeks back.
the waste gate is sealed by a "penny" (common name)
look here
if the turbo is working normally to a certain boost pressure then i'd hazard a guess its a actuator problem, e.g split diaphram in the actuator. but difficult to say without seeing it