Boost creep issues are usually WG related issues such as it being too small, the door not opening fully, etc of that nature.
The actuator may cause boost spike issues if it's old...if maybe that is what you are referring to?
I have simba's CT27 now with a stock WG and full 3" exhaust. What I notice is the WG door does not open up fully due to the XS Power downpipe. Even then, without a boost controller, I don't have any boost creep or spike issues...maybe I creep a psi or so but nothing towards 18psi.
Bryan