Is there a device like a manual boost controller that has a fixed value? Like just preset for 20lbs period? No valves or adjuments of any kind? Seems like it would be easy to make such a thing and it would be very stealthy. I guess it would be a fixed value pressure regulator. If anybody knows of such a device, please let me know...

 

It's called a wastegate spring. They come in different 'sizes' and will only allow the turbo to boost to a preset level. I've read the Evo has a 10 psi wastegate spring. The extra boost is achieved with the factory boost control solenoid. I don't know if you can get a 20psi spring the the Evo turbo.