The terms "Holley" and "MPG boost" in the same sentence???????? Boost over what? a 15 year old pouring gas into the intake out of a boot with a hole in the sole??? :p :p :p
Don't know what you had previously on your 305, but if you get the Holley within 75 percent of the fuel economy to be had with a q-jet you need to open a tuning shop. Your services would be in great demand!
As to the smile, unless you have a bunch of mods to the 305 a properly tuned Q-Jet will provide a much larger smile!
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But to each its own. I hope you are happy with your purchase.
Jon.
