I designed this to allow me to switch from MBC control to ECU control. I’ve tested several designs and I have found this to work very well. I have more details on my site.

http://www.lehigh.edu/~erp4/saab/Upgrades/BoostControl.html

http://www.lehigh.edu/~erp4/saab/Upgrades/DualControl.jpg

can i get the solenoid from a local hardware store or only online. Also what is the solenoid for? What should I tell the workers I am looking for?
THanks

You probably will not find one at a local hardware store. The important specs for the solenoid are that it must be 12 volts DC and be able to handle at least 30 psi. The link I have on that page to the solenoid valve is a good choice. That valve will work well, I use one for my water injection system. It will require two hose barb fittings.