I never doubted you. Just saying the 35 r is over kill if your only looking for 400whp on e85. Hopefully 8 psi isn't full boost for too long.
This size motor will make that size turbo be at the beginning of its efficiency range very easily, at 8 psi. Being automatic, the extra load on the engine is going to make it spool quicker than if it were a manual.
Similar setup on an Infinity FX35, which has a slightly smaller motor, boost was nearly instant. Acted more like a roots blower. So my speculation for Toon's build is most likely a bit conservative.