Originally Posted by Here2Go

Well - I'm down a few hundred miles from you just above FL and I normally boost around 14 @5,500 RPMs.
I don't usually tax my Mini on a daily but I have hit 16 @ wot (6,500 RPMs) on a few occasions during colder months.
So boosting 10 w/15% pulley seems like something is stifling.
I had some issues with a surging/jerking feeling a while back when pushing the car @ WOT. It was suggested that the usual suspect of this symptom was the bypass valve.
I bought a new one and was prepared to install it but decided to replace my MAP & TMAP (easier to get to) with $OEM$ just to see if that might be the cure. It was. An expensive (OEM) cure for just 2wo little plastic plug-in thingamabobs.
It was recommended to purchase OEM because most others/cheaper brands fail or are defective right out of the box. You may want to try cleaning your MAP sensors with electrical contact cleaner or isopropyl alcohol first to see if that helps.
Just be sure not to mix them up. TMAP and MAP look the same but are different.

I am not a mechanic. Just mechanically adept.
Not sure if cleaning or replacing the MAP sensors are the answer to your particular issue. But hoping for a simple fix for you.