How much experience does he have. You have to remember that some of these guys, although "certified", doesn't necessarily mean that they are good at what they do. It's just a name plate being called certified. Personally, I would never let anybody but Yoshio touch my engine management system as it is one of the most vital components of a vehicle. Yoshio has a proven history of engine tuning and racecar building. On top of that, he's a "certified" Toyota tech schooled from Japan. Even furthure, he can read those HKS, Trust, Blitz, etc., Japanese instruction manuals that come along with your performance parts LOL. He's definitely NOT you're average tuner. So IMHO, there's no reason NOT to go to him. Pay a premium once to do it right, or pay a lot to do it dozens of times. I'd choose the first one. But it's your car and whom ever you choose is your business. I just hate seeing people trying to take shortcuts and finishing last. Not to mention having their pockets emptied from half-ass jobs when they could have paid the premium to have their cars done professionally.
Should keep that in mind...
Xoh