Hey Cravnpup,
The following is a result of my personal experience, added with comments from those I trust...
I don't know about the velocity tube, but with my K&N, Rousch Cold air kit, and Pro-M 87mm MAF (which is calibrated for the stock injectors), I did get a small boost by "seat o' the pants" feel at high RPMs without a larger throttle body. Most folks I talk to say that the throttle body just isn't worth the cash unless you add an after-market intake (such as the Ford Motorsport unit) with it.
I plan on purchasing one when I have the cash for my motorsport intake\heads combo.
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1998 Mustang GT
13.97@103
"Traction Impaired" or "Nitto Needy"
Pilot Proverb:
If all you can see out of the window is ground that's going round and round and all you can hear is commotion coming from the passenger compartment, things are not at all as they should be.