Best results will come from a Dyno tune. Your concern about "one blast" isn't really correct as most reputable places that tune street cars will spend heaps of time tuning low/mid load areas to make the car feel good under normal driving conditions, and only then will they move onto power runs and high load tuning. A reputable tuner will factor in safety margins for real world ambient temps and humidity levels if they can't be simulated on the dyno.
You can try an internet tune but this can be risky as there's less monitoring of the car while you're testing the tune than you get on a dyno, so it's harder to tell when things aren't going right, and the final results of an internet tune will never be as good as a dyno. In saying that, there's an internet tuner out there that's specifically mentioned by Raptor as providing quality tunes, so you can research that and come to your own conclusions.
Headers can get you some extra gains from any tune as the factory ones are highly restrictive, but are apparently only worth it if you free up the rest of the exhaust system as well, which makes sense.