Yup, concerning the installation and tune, in our Mustang Klub of Poland we have quite good member tuner working on HP Tuners software. He already tuned many of our cars including mine. The good thing about it is it's not a "standard" tune, but the tune done for a specific setup in a specific car (with sonda in the exhaust, live logging, etc.)
He also builds and tunes motocycles and builds turbos for other cars -
HD Customs
He said he should be able to install and tune for reasonable money.
If you have not found it yet,
HERE is quite a good write-up about very similar On3Performance turbo Kit installation in a GT.
As I said before - before I decide to buy this kit I'd be very interested in the results of any of you if you got tempted to install this
I think that 3.73/4.10 gears + this turbo Kit can turn our V6 into quite fast beasts beating stock GTs with ease...
PS.
VORTECH is an option too, but if I read correctly, the On3Performance turbo kit should provide more potential than supercharger. The high output VORTECH is already 1k more. Depends on who prefers what - I like the idea of keeping the mileage and using the power only when needed. The gear swap should improve the low end where there is no turbo boost yet...