[Ikestaa]

You might want to check out Sport Compact Car. About a year and a half ago they ran a series (about 4 issues) all about turbocharging. They offered all kinds of equations to help you figure out how much boost you can run as well as different aspects of the turbo: b-width, trim, inlet/outlet size etc. etc.

There are some other guys on the forum with twin turbo cobras, so I am sure you could talk to them about it.