I had a similar problem with mine. Would rev fine, but wouldn't boost if I pressed on the throttle hard, so its power was restricted. Mine's an auto, if it were a manual it'd feel like it couldn't rev. Apply throttle slowly and the boost comes on.
I replaced my turbocharger with a Forefront unit and it's perfect.
You need to be sure it's the turbo. Check vac hoses etc, but use a tool to monitor boost pressure. If applying the throttle hard causes the turbo to 'stall', it's possible your turbo's bearings are worn causing the shaft to reach a certain rpm then wobble if it's loaded too much in one direction (and at a guess I'd say the turbine end of the shaft, because the large force of the exhaust hitting the turbine would be the one putting the shaft to the side).