This engine is really expensive to be modified. The Colombo & Bariani Stradalle Massimo Cams are cost ~1800Eur! Then you will need some improvements of your engine heads - gas flow, port polish etc. Thsi will cost you at least 500Eur for both heads. Then maybe a good stand alone ECU - Omex or Autronic, Mega etc....As i told expensive expensive.
For this amount of money you can go for Supercharger upgrade. Rotrex systems are great and costs between 1500 - 3000Eur. The bhp gain will be better, car feeling will be better, and you can still drive your car daily, and with less fuel consumption.
Alfa Romeo 166 2.4 JTD (GTB2256V, Extreme remaped, 1.7bar boost, straight exhaust system, Brembo 4pod brake system 330mm brake discs); Alfa Romeo 145 QV (Colombo&Bariani 272 cams, Extreme remaped, JR cone intake, 240cc Saab turbo injectors, Supersprint 4-2-1 manifold + cat back system, O.S.R.A.V. Sport Kit suspension)