I'm no turbo expert either......but if the stock CT12a's on a 1jz can "flow over 400Hp" why are there so few 1jz powered cars on standard turbos with 400Hp??.
If mine could do that so easily I wouldn't thinking of moving to a bigger single turbo!
And really...who want's to beat NA Supras with a turbo-ed car. If it was that good it could beat most 7m turbo and 1jz-gte powered Supras....I don't see that promise being made anywhere in the sales pitch!