They are located using pins and an actuator on top. I can't see why you couldn't just cut them off to be honest with you. Ok its a bit brutal.
But unless you take the inlet off and then seal the holes.
Your one won't have the swirl flaps unless it is a really late 2005 156 Sport, the early CF4 (147, GT and Sport 156) cars have an aluminium inlet manifold with plastic swirl flaps, the late CF4 (2007-on GT, 147 & 159) has Plastic intake with metal swirl flaps, these metal swirl flaps are only held on by 2 tiny little welds
So knock the welds off and then remove.
I don't see any reason why you can't just remove the flaps from the spindles
Anyway - Its an option.
Alfa 166 2.0 Twinnie - LPG and a few trick performance parts