GT17 too small?

[cali yaris]

considering the cost of a piggyback and a tune compared to the cost of a turbo

Another problematic approach (so far) -- piggyback didn't work for me and several others. Doesn't mean it can't work, but you posted this (I'm guessing) without real world knowledge of a successful application on a Yaris. Another indication you are drawing from other-car experience, not specific to the Yaris, and also an indication you haven't read the other threads about tuning these cars. Not totally irrelevant, but not all that helpful either.

Sorry about the post count snipe, but you pissed me off. I found my happy space again since then.