my personal opinion and suggestion - steer clear of turbosmart eboost
i have one at the moment and have had one for a couple of years, and although it does its job most of the time, i still didn't have an easy run getting it set up, and sometimes it still isn't 100% with boost stability.
1) its a prick to set up right - have had two people set it up on a dyno and it still spikes/isn't stable - could be other factors i guess...
2) eboost are overpriced
c) i know of someone else with a GSR, and someone with an xr6 turbo who have both complained about them in their cars / setup issues / boost stability.
ive heard great reports about the electronic boost Profec B controllers..but havent personally used one.