227hp in a V5 I managed a 12.5

270hp in a V5 managed a 12.2

260hp in a 05 STi managed a 12.8

320hp in a 08 STi managed a 12.2

360hp in a 08 STi managed a 11.8

I'd say your 2013 STi with 300hp should net a 12.5-12.7

Hope that gives you some sort of guide from my previous experience.

Goodluck!

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[ESTEYE]