I don't claim to be an expert and I may be wrong about this.
The dpf needs to reach a high enough temperature to effectively burn off particles, this means that it works better the nearer it is located to the manifold. On some cars where it can't be fitted close enough to reach these high temperatures, a fuel additive is needed to lower the temperature needed to burn off the particles.
I know this is not the case on Alfas, but maybe this product could help.
Either that or add the cost of this to the extra fuel used by regens, and spend it on a remap and bin the dpf.