Sorry for the delay - I've been up at Mt Panorama again for a motorsport event and am still catching up.
Absolutely - hoses allowing the vacuum to leak will cause the turbo vanes to not be opened as much as expected = less boost.
EGR cooler leaks - if enough exhaust gas is leaking out of the EGR cooler then that pressure isn't driving the turbocharger and again, less boost.
The last thing (because it's the most expensive) to look at is the turbo itself. It doesn't hurt to do a couple of preliminary checks:
1) Undo the clamp on the intake of the intercooler and wipe your finger on the inside. Now examine the contents under a bright light. If you notice any metallic flecks in it, your turbocharger is either wearing out a bearing (gold flecks) or the bearings are bad enough to let the impeller rub the housing (silver flecks).
2) Take the intake hose off the front of the turbocharger and give the shaft a wiggle and a spin. It should be smooth to spin but shouldn't spin forever while not being difficult to spin. It shouldn't move from side to side too much at all. If there's any significant sideways movement it's likely the bearings are done for.
In either case, it MAY be possible to rebuild the turbo with a kit that contains new bearings and all the seals. There's no guarantee this will make the turbo 100% (particularly if the impeller has been wearing) but it will cost less than a fifth of a new turbo.
3) Attach a new piece of hose to the actuator and suck on the other end. If you can't make the arm move, either the arm is (or vanes are) jammed or the diaphragm in the actuator is damaged.