Then increase the values! That simple. Eventually, you'll be running 100% WGDC. If you can't hit target boost with a 3 port at 100% wastegate duty, you have another problem. 3 port or blocking or interrupt solenoids allow ZERO boost to reach the wastegate at 100% DC.
If you put 450 in your map and still can't hit target, it probably means you need a stiffer spring, have a leak/crack in the turbine, boost leak, etc.
3 ports allow a full envelope of performance. 100% boost to the wastegate actuator all the way down to none.