Will a boost controller not control the boost creep? If you set it at a specific psi it is suppose to release the excess air to keep at a consistent psi?

 

boost creep is the inefficiency of the waste gate to bypass all the exhaust energy form the turbo.

 

To answer your question, no. A large wastegate can though. Your theory is correct however if the wastegate is too small then the boost controller can't let that excess air escape.

 

It will not control the boost creep.

If your stock turbo is having boost creep problems then porting the wastegate will help.
http://fc3spro.com/TECH/MODS/TURBO/wgp.htm

A boost controller releases the air pressure acting against the wastegate spring, fooling the wastegate into INCREASING the boost level.
http://www2.turbov6camaro.com:443/gate.htm

 

if you have an S5 turbo, port wastegate and bypass stock boost controller. Set to wastegate boost and it will not overboost. Much.

 

A boost controller can never lower boost past what the wastegate will naturally achieve.

Boost creep is caused by insufficient flow through the wastegate, which is a physical problem and cannot be compensated for by a controller.