ECU Flashing a Merc 250 Pro XS

Anybody know of a place around DFW that can Flash a Merc 250 Pro XS? What does this usually cost to do so?

I want to get another 50+ hp at the prop. My boat has an Unlimited HP Rating.

Sorry, but a flash alone isn't going to get you 50HP, no matter what they claim. You're better off investing in a 300 Pro XS in the long run.