For example I hit 23 psi at peak, then taper to 20psi by 7000rpm, and down to 18psi by 7600rpm at cut off.

So am I running 23psi? or 20 psi? Or some different number?

Your running exactly at what you just said. LOL

23 psi tapering to 18 psi.

The thing is that people usually just give out one figure.

Also 3psi loss and 5psi loss is a huge difference.

When people say '4psi loss average for stock turbo and pipings' I think they usually mean only up to 7000rpm, instead of 7600rpm. Can anyone clarify this?

So still unsure if I shoul say

'My boost is set at 23psi'

or

'My boost is set at 20psi'

and

'My peak boost is 23psi tapering to 20psi'

or

'My peak boost is 23psi tapering to 18psi'

Most people refer to their peak boost as the boost they are running.