Actually Jack, a MBC will not let you hold boost solid to redline, even at 19 psi. I know, because I have one.

People are preaching that the stock turbo just "isnt efficient" enough to hold boost to redline, but that's a lie. The turbo is plenty efficient, and will hold a max of about 26psi to redline before running into efficiency issues.

The only proven method I have seen that allows you to hold boost solidly through all gears and rpms is upgrading the wastegate actuator.

 

what kind of waste gate actuator are you talking about anway ? is it forge??

 

It depends on ALOT of factors, but I do have an MBC on my car that holds a solid 21psi through redline. I do prefer closed loop electronic boost control however..

And the stock actuator can easily hold 21 psi (and more in some configurations).. Most actuators have not been correctly preloaded which is likely the reason why they aren't holding correctly. Also, 80% of the cars have other issues, boost leaks, inadequate signal to the DV causing it to open early, insufficient spring pressure in the DV, etc..