blow off valve/bypass valve
I learned a lot from Corky Bell's book on supercharging/intercooling called "Supercharged". Any bookstore has it or can get it, or online at Amazon.com for like $18. Worth doing a little reading, even the basics, and maybe save $2000 or more. He talks about bypass valves with diagrams.
Even if you don't decide to work on it yourself, some knowledge will help prevent some shop from ripping you off.
I hope the project goes well.
Jim


