stronger actuator... (std is 5psi) will hold boost longer providing the compressor is still keeping up..
12-15psi is the range for uprated ones, but n75 duty cycle control WILL have to be changed to avoid the thing spiking boost to the moon and windowing your block.
I think forge have a piston actuator now.. Not used one myself, used their diaphragm ones before.. The plastic bush (blue thing) can melt in k04 environment, but they can do a phosphor bronze one also... Check with them which they will build as std... and if not std, ask for it. Travel is less (or was less on the diaphragm one) than an OE actuator, so choose the correct spring rate and dont rely on adding much preload to it as it will rob the already reduced travel. The piston one I dont know, so cant comment to its travel. I may ask for one to chuck on lupos hybrid to see.
check that your mapper can accomodate a wastegate x3 stronger than stock for the n75 control.