I'm on their mailing list and they sent me their 'updated' catalog about two weeks ago.
This catalog wasn't any different from the last one.....
The Garrett stuff is a LOT more bread than your run of the mill Holset, Schwitzer turbos - this is probably the reason not too many people have plunked down the $3k+ to experiment with the large frame GT series turbos from Garrett.
The plus side of the GT series being available is that the T-series stuff has come WAY down in price.
There's a lot of 'trade secret' type of stuff involved with turbos... . amongst other things..... so getting any nitty gritty information out of anyone will be difficult.
Matt