And that 16+ hp is meaningless.
I don't think I've met anyone who would turn down a 5%+ bolt on. Have you?
Given the OP was about the gain from an intake swap on an otherwise stock 340 - a more constructive question would be, now much gain is a reasonable one for only a manifold swap? Obviously something with headers, heads, and more cam would see a bigger gain, but for a stock motor?
Personally I think 16 hp is worth every dollar that an air gap costs, especially knowing that the later addition from headers, carb, and cam will be even greater with the intake there.
Then again, which is worth doing first? Intake, or headers?
Personally, I'd probably start with headers, then intake, but if I pull an intake I'm not leaving a stock cam in it.. That's just me.