American muscle offered a free tunes for life when I bought mine. Is definitely worth it if our slow about adding extra parts. As far as noticeable power adder alone? I don't personally think it gives much performance gain (5hp?).
BUT, on the other hand if you intend to install extra parts along the ownership of your car, it definitely will help the extra parts in to "mesh" with each other.
And the 3-3500 whoosh you feel isn't about the tune, but more the butterflies. Get a charge motion delete plate and pair it with a tune and you'll have a smoother powerband all the way throughout the RPM's!