Did someone say Throttle Bodies???

[98GtPower]

So I have been contemplating getting a larger throttle body for my 98 mustang gt. But my friend said that in the mechanic school he went to they taught them that putting a larger throttle body on late model mustangs decreases the efficiency of the car and it will run slower and crappier with it on. that is unless you put a supercharger on. Any experience with changing to a larger throttle body on a close to stock engine??? And what should i get 70mm or 75mm??