More air + the same amount of fuel = lean. Seen it on the dyno for my car.
TB might be a good mod in conjunction with SAFC-II, reflash, Piggyback ECU. Otherwise, you might just be putting the cart before the horsepower.
Why did you bump a 5 year old thread to bemoan your customers, few of whom still post here?
Also, while your statement is true that most intake mods probably don't need a retune, a larger throttle body is probably the most sensitive part to increased diameter (mass flow equals density * area * velocity). A change in throttle body area will need at least it's signal remapped.