If its low on boost, check the actuator is correctly pre loaded and functioning, ideally pressure test the actuator and see what pressure the gate starts to open, this will give you a good idea of spring tension.

Check the Amal is functioning, correctly plumbed and correctly jetted,
Check the amal has a 12v and a control feed to the ecu

After that being very carefull and measuring fuelling while doing so, pull the actuator pipe off and bring it on boost, this should keep the wastegate closed, BE AWARE THIS SHOULD MAKE FAR TO MUCH BOOST. So do not hold it open or engine damage mar occur, just squeeze it onto boost and see if the turbo itself can make more boost than you have.

If the boost is still low with the pipe off, the turbo is faulty or you have a massive air leak.
If the boost is high, its simply a control issue, so go back through the first part.