You didn't say whether manual or automatic; I get similar results on my S70 T5SE automatic, and like you mention in your later post, have spiked at 17 plus under rare circumstances.

My ECU seems to step-up boost depending on conditions. From zero, typically I see around 4psi sustained / 9 spike until the car is moving, then 9psi sustained / 14spike.

I spiked 17+ twice under identical conditions in exactly the same spot: already doing 50 and "dropping the hammer" to pass a truck on a two-lane rural road. This is actually a little scary as the torque steer just about wants to flip the car onto its roof, and in just a couple seconds I'm already well above of 80mph.

BTW, located my boost gauge in the ashtray bay, just ahead of the shifter.

Yep normal. Non of those devices can or will change turbo boost.

Sounds a pinch low, but not bad. Depending on what gear you are in, you will get different peaks, as you should. If you can, floor it at about 80km/h and let it go. You should be able to get a bit more at the 80-120km/h range when the pedal is on the floor, then you should off the line.

As for your spikes, it sounds a little high considering your max boost is around 10-11 psi. Did you tighten the wastegate?