What would 1 pound of boost be worth on my setup (1 lb = ?? HP)

440 approx 450 HP - 9.5 to 1
all iron with ported head
Blow thru - 88mm garrett

on my iron [346]head it was about 40HP.i have to dbl check.mine flow 280/180 at .600lift,my cam is .646/.631 lift.your result may very.it could be + or - 10hp of that depending on the head.

it really depends on where your putting that 1psi on the turbos map. and the compexity of the setup, thier too many varibles to say really what you would expect, also you could dyno the exact same day exact same setup and see a 20hp difference or more.
heres a couple of my expierances
srt4 stock turbo 20psi 294hp
srt4 stock turbo 22psi 303hp
srt4 .50 trim 22psi 391hp
srt4 .50 trim 24psi 429hp
srt6 16psi 287hp
srt6 17-18psi 310hp
cummins 70psi 814hp
cummins 72psi 820hp
cummins 75psi 855hp
cummins 80psi 909hp

As a ballpark way to think about it, standard atmospheric pressure is 14.7 psi. Add on PSI with boost and you add about 7% to air density and power. If you start with 450 HP 1 psi gets you 7% or 30 more hp.

1 pound of boost would be worth about 20% of the actual 5 pounds more boost you know you want to add. You say 1 now......

Unfortunately the power increase vs boost pressure equation isn't linear. The more boost you add, the less you gain per pound of boost added. I went from 10 psi of boost to 18 psi of boost - and on my combo it only gained roughly 100 hp.

Dropping from 17 psi to 8 psi cost me 200 hp. I also dropped a little alky spray when I did that so it factors in a wee bit too.

I was just boost stacking it into a zero gain.

With my single T4 .96 A/R hot side and full 3" exhaust system - it simply can't get any more thru it and I think it's trying to choke it off at speed. I gots lot of stuff go fix before it'll go any faster.

I be trying to push it thru a straw.
I probably didn't have enough fuel for it either.
I guess I should only expect so much from 24# injectors? LOL

last I checked, 1 lb of boost is still worth 1 lb of boost.

I would think you'd also need to take into account, how much hp you spend to make that extra boost. Extra backpressure on a turbo set for higher boost and extra drag for turning a higher geared supercharger.