2009 Mazda3 Sport stiff clutch after high revs when no gear is engaged
 

Hi,

I have a manual 2009 Mazda3 Sport (185 hp 2.2 Diesel) and I have an issue where after revving the car either in neutral or in gear with the clutch in, the pedal gets really stiff around the biting point.
This happens both at a standstill and while moving. The issue fixes after depressing the pedal a few times and then it's back to normal but happens after every time I rev the engine.

There are no issues at all when any gear is engaged and I'm accelerating hard, even to just before redline.