Have you tried running that much boost without the controller? Surge would more be pointing towards bad turbo spec...well bad in conjuction with you engine spec i mean, not neceserily a bad turbo full stop.
Personally the only prbelms i had with the avcr was it had a tendancy to let the boost creep just a little over what it was supposed to be and you were forever fine tuning it. It mega time consuming but well worth it if you use the facilties this controller has.