Power Delivery issue? B9 RS4 limiting power at 50%, even at kickdown

[firecloud7]

I've had this issue the last couple of days and I have no idea what's causing it- I'd appreciate anyone's informed 2 cents here.

When I push down on the throttle, even down to kickdown, the car shifts down, revs high, but doesn't deliver the usual power. According to the power gauge on the dash, it caps out at around 50%.

It's happened all day today, even when the engine is already warm and there are no limiters on the car (as far as I know).

Would appreciate hugely if anyone could suggest what's going on here.

[SuzaFan]

Maybe leakage/crack in turbine hose/faulty blow off valve?
What is your boost gauge showing?

[Jools]

Is the limiter on RPM or speed?
On the cruise control stalk I have a switch that can turn its function to a speed limiter instead, have you accidentally caught the switch?

As you accelerate hard watch the boost pressure on your dash (mine is bottom right) I would expect yours may not be building pressure as it should.
I would think this would be as SuzaFan says a blown off or leaky induction pipe, or you may have a vacuum leak on the turbo side, or a failed / sticky turbo vacuum actuator.

I have added a couple of images of the pressure and vacuum side of the turbo's.