It's not just the SVTs! My regular ZX3 has a real lazy response at first, and (luckily if you can call it that) I stripped out the threads on the original intake manifold; and ordered a new one to replace it... the seller offered to port-match. The 65mm Focus Central throttle body matched up perfectly to the intake manifold flange!
The response was a night and day difference: it still takes a few days re-learning how to work the pedals when I buy new shoes or boots (the soles are thicker), and the engine flies up through the revs before I can even feel my foot on the pedal. And after I swapped a getrag in there with a lightweight flywheel... whoa!