how much horsepower gain for 52 and 58mm LT1 throttle bodies?

I've done searches all over the net and everybody talks about the added power but no one is specific about exactly how much gain is possible. Being that these things can cost over $500 I'm not sure it's
worth the bucks... can anyone vouch for how much power can be had from these things to justify their cost (and labor, since I'd have to port for the 58mm on the LT1)?
Thanks!
Rob
PS: While we're on the topic, how about the throttle body coolant bypass mod? Anybody vouch for this one?
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doubt you would gain anything without more air flow from cam, porting, and exhaust to go with it.
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