Forge MBC
 

It "clicks" when you turn it so its easy to switch between boost levels. Has the soft spring in it, lost the other spring. I ran 26psi with it, would go higher but not sure how much. Comes with mounting bracket.

$40

Re: Forge MBC
 

For the record, mine with the soft spring would not go any higher then 21psi. I also lost the stiff spring. I emailed them and they shipped me a new one free of charge. Great service.