The spring in the stock actuators, unpreloaded, usually allows the flapper to go full open in the 8-11 PSI range. The FP 18# HD WGA, unpreloaded, lifts the flapper full open by 14#. The FP 25# HD WGA goes full open by 18 PSI of boost pressurre, unpreloaded.

So, by switching from a stock MHI actuator to the 25# FP unit you are gaining roughly 10# of base spring pressure right off the bat.

 

EDIT: i deleted this post as i had written it on my iphone while driving and it made no sense to me whatsoever once i reread it.

 

Stock wastegate. Replace the spring, or do the spring mod and that might get you a spike of 32psi. Don't expect to hold anywhere near that. I hope you are also on ARP head studs and bolts.