See around the 6 min mark http://youtu.be/6Sivt84RuTk
Wowwww that's awesome
Not sure if they are variable vane turbo's (it doesn't look like it) but it does look like they have twin scroll (or more) exhaust housings with a flapper/valve that directs all flow through one scroll for quick spool and lots of low end grunt.
Oh how if love an SLS machine.