Greetings, I had heard that at one point in time a company had made tuner chips for the ECU on an EA82T engine on the turbo XTs. Anyone know where I could acquire such a tuner chip? Or if there are any new tuner chips that the ECU in a XT Turbo would accept? Thanks.

There was a company in australia/new zealand many years ago that did it, i doubt they're still in existence or doing it.  maybe the down under boards/forums/members know or have mention/record.  or look up their model names for similar vehicles (like the loyale's equivalent or whatever since those were more common than XT's) and search for those. 

in the 90's the EU models were said to have higher HP and it was due to injector/ECU differences, if that's true those could be sourced for improvements.

if the turbo/intake/exhaust/intercooler/engine tune are maximized and that's not enough, an ECU tweak isn't going to add enough to make someone going through all that expense/effort happy either.

I'm not aware of any chips available for any Subaru prior to the Legacy.  The EU-delivered EA82s supposedly had a different ECU, but I think the horsepower difference has more to do with those cars not having catalytic converters compared to N.A.-delivered vehicles.