I was unaware that Diesel engines had a "Throttle Body"..Usually, their air intakes are unrestricted. Engine RPM and power output are controlled solely by varying the fuel injected into the engine.
When small, high-output turbo-charged diesels run up against stringent emissions regulations, these are the kind of problems you can expect...If you are not subject to emissions testing (other than a simple visual check for smoke) I would disconnect and block off the EGR system and if the vehicle operates satisfactorily, stop worrying about it and drive on...
Thinking about this, the "throttle body" may be the point where the exhaust gas is injected back into the engine and this may be combined with a turbo "waste gate" , a device to limit boost pressure..
If you intend to keep this vehicle, YOU may need to educate yourself as the the finer points of its design and develop the skills necessary to maintain it yourself..