I'm super confused. All 9-3s came from 900NG, which was made during 50/50 ownership on GM-platform (Opel Vectra). SAAB had a habit of throwing away half of the platform and doing things themselves (see 9-2X). Go check your coolant expansion tank cap, it will literally have GM logo molded on it. Maybe your mechanic (or you) didn't realize you can look up parts by their GM number instead of SAAB's.

Sure there weren't "American parts", but there are a fuck ton of GM parts. Opel had been a wholly owned GM subsidiary since 1931.

Also why are you calling it 9-3t? There was never 9-3t and all 9-3s sold in the US had turbo.

I'm in the "what could 1 more turbo hurt" stage ;)