I'd go with a tuner first. I would also choose a tuner that allows you to have modified tunes downloaded from the internet for when you decide to go with propane. This sure beats having to send your tuner in!
The Predator is the only one that I know of that performs these functions.
For the sake of convenience, a tuner might be the way to go. But, for maximum performance, you can't beat a custom programmed flip chip.