[kjewer1]

The reason to upgrade the actuator is to keep the flapper from blowing open prematurely. The t25/28 has a very resitrictive turbine housing, raising pressure on the manifold side of the flapper, which then pushes it open (force = pressure x area). Another reason is to allow EBCs to run more boost (most do double WG spring pressure), but this is unlikely to be a reason to do this on such small turbos. Also, running more than double spring pressure with an MBC can lead to very unstable boost.

I installed a Forge 17 psi actuator on my EVO8 turbo. No change in the max boost I could run, but it was worth the 150 bucks to rule out a flapper blowing open problem. The EVO8 turbo seems to be designed very well since it doesn't blow the flapper open at up to 28 psi.