If you've checked the turbo and it's fine, your problem is more likely to be boost leaking somewhere.
Assuming that there's no intercooler, boost will leak from:
* cracks and splits in the hoses. These are often NOT visible on inspection but under pressure the hose will expand and the cracks/splits will open.
* Undertightened hose clamps. These will be revealed by being loose as the oil from the blow-by will get in and lubricate the hoses rather well, and that oil will spray around much of the perimeter of the join. You need to completely separate the hose, clean both faces in a solvent (metho/petrol), allow to dry (metho = 10 seconds, petrol = 30 seconds) then reinstall and nip the hose up a little more.
* Overtightened hoses. Too much tightening will cause the hose to pinch at some point and boost can leak out. If boost is leaking so is oil, so you'll see a tell-tale thin spear of oil coming from one point. You will have to remove, clean and reinstall unless the pinching has damaged the hose.
* Cracked EGR tube with exhaust side blocked. These tubes look a lot stronger than they are and rival that cheap toilet paper you find in rest area dunnies for strength. The easy solution is to block both ends, ensuring that you use a good sealant, and toss the pipe where it belongs.
* Damaged EGR valve/leaking gasket. Again it's easy to spot - look for the oil. If it's leaking there'll be oil - guaranteed (unless you have a catch can). Not so easy to fix if it's the valve itself, the valve can't go missing without the car bitching at you about it.
Don't rule out turbocharger failure just yet, the turbo can feel right but have blade damage. If the other less expensive things to check have not turned up anything, then getting someone to have a good look over the turbo is next on the list.