Originally Posted by angelofrat42
Although the power difference wouldn't be very different, I would have to say that having it professionally tuned by a good tuner is a much safer bet than a hand held. Handheld tunes are quite cookie cutter one size fits all so you could potentially be running too lean or rich. My car has idling problems that would be fixed with a dyno tune, just don't have the money for it or I would get it done.
Or you can make logs of your car running and send them to the company that does your tuning and they can further tailor the tune for your car.
I don't recommend a dyno tune until you have finished with the car. Else wise your sinking money multiple times to get it tuned. You also have to find a good tuner for mustangs. Around me I mostly have shops that work on GM cars and they cannot tune mustangs for anything.
Plus, when I got my car dyno run at the local speed shop they were amazed at how smooth my Bama tune was and how perfect the A/F was.