Definitely DO NOT be unhappy with those numbers. Heck man, first off your right in there (pretty close) to what other guys with your mods are running (minus the fact that most of those guys are driving automatics), but you gotta keep in mind on top of that your dyno guy said that dyno typically reads a bit lower than other dynojets, AND it was hot as heck! So you factor all that in, and your doing well.
If your car was an auto, you would have probably dyno'd 10 HP less than that. Be proud, that your driving a V6 putting around 340HP/300TQ out at the crank (well maybe not that much on a HOT day lol)....maybe even a tad more.
If I was you I'd go back on a cool day or this fall when its about 50 degrees out and give it another go...of course if your E85 tune works, you'll be makin even more power.
5th gen IS SOLD! 6th gen built 10/14!!! Can't wait!!