The issue isn't drafting per se, but the unevenness of the draft. When you draft, the iBike's pressure sensor will correctly notice that wind pressure has fallen and adjust power accordingly. The question is whether the draft is even enough that the iBike's single reading at the handlebars is representative of pressure all over the rider's body. I never saw an issue when I drafted, but I don't draft much, as most of my riding is training and it's done solo. I've heard others claim that it's noticeable in small groups with a narrow draft but less so in packs, where the draft is broader.

It has two, one absolute (barometric) and one relative (stagnation pressure), but only the relative one is used in calculating power. The barometric sensor is used to record altitude just like a Polar or Ergomo. It *does* use the barometric data to calculate air density, which in turn is used to convert the stagnation pressure into a windspeed. But power calculations go straight from the stagnation pressure reading.