Just a reminder... This "mod" isn't a long term power adder. It is faking out a sensor to make the car think it is colder out than it really is. This "mod" only works on the engine (if at all) in very specific conditions, and the gains will be minimally noticeable at best. Now changing a pulley size, or adding headers, or freeing up the intake are all true mods - as they effect the cars power under any conditions. GM would never have to do something like this if they wanted to. They make the PCM'*. They can just program the differences into the tables at the factory.
And as far as the performance and power of the Bonneville goes... (this hurts a little to say)
....the Bonneville wasn't designed as a strip or street drag car. It is a family sedan, 4 doors, daily driver that Pontiac made. A family sedan doesn't need 600hp for the majority of buyers, and in fact, that would most likely deter more than it would draw. Now all that said, I do plan on suping mine up as much as possible, but this will not even be considered as one of the mods I do.
(steps off the soap box)