With this being a true Cosworth, the engine mods were probably the following: Cosworth heads, pistons, and crankshaft. No mention from any of the articles about any work done on the turbocharger. Back in 2010, Borg Warner partnered up with Cosworth to put out turbochargers.
The people that did the Sema car is out of So. Cal and the name of the company is M&J Enterprises.
They have a link that's still being worked: MnJ Enterprises - Project Vehicles