I've got the same issue on my 2.4 20v - heavy smoking under heavy acceleration, mild smoking under mild acceleration (so it's not the "normal" diesel smoke when flooring it). The EGR has just been replaced, but it didn't cure the problem - I'll check the pipe tomorrow and if it's that, my current indie mechanic will have one very unhappy ex-customer.
Funny enough, I believe the amount of smoke is also influenced by the (supposed) fuel quality - I could swear the car was smoking less when I filled up with Shell V-Power something instead of the usual OMV diesel I'm using. But again it might have just been placebo.
One partially unrelated question - at what RPM do you guys shift gears? The reason for which I'm asking - in order to reduce the amount of smoke sent out when shifting (obviously more at low revs), I've changed my shifting habits from 2500 with a cold engine / 3000 rpm with a warmed-up one to about 3000 rpm higher for each occasion. Am I doing something wrong there?
Totally unrelated - just completed at 2500 km trip across Germany and Austria and the Alfa didn't miss a single beat. The only problem was me scratching one alloy in a very tight parking lot.