A dyno tune isn't the best option either.
With no changes at all I've made up to 5hp difference with my car on a dyno doing back to back runs.
The 0-100hp differences you see in dyno's can easily be attributed to error, or margin of error.
It's something that has to be taken into account at all times.
Don't "think outside the box".
There is no box.
Do it correct, or do it twice.