It has to be done with the computer installed on the vehicle. You should go to the dealer and maybe talk to the manager or something, because it's a very simple procedure that takes less that a minute. All the tech has to do is hook up the tech 2 make a couple of selections, step on the brake pedal, shut if off, restart it with the brake pedal still depressed, and rev the motor till it hits a limiter. It's has nothing to do with programming it just enables a feature already built into the computer. You might have to be pushy with them and say a friend of yours just had it done with no problem.
The problem with dealerships is that alot of them don't know which way is up. I'm not saying some dealers don't have some real savy techs but the majority of them are just part changers and some service managers know nothing. So they might not even know ho to do it.
Or you could find someone in the area with hp tuners or efi live.