DPF regen EGR ECU remap
Could your car have already had a remap that can't cope when the DPF regen happens?
When I first bought my '06 1.9 JTDM I had horrible juddering, spluttering, and stalling during regens.
The indie specialist I bought it from replaced the EGR, did forced regens on the DPF, and arranged for a software check/update at an authorised Alfa service agent, all of which solved nothing.
The car went like the proverbial off a shovel, so it seemed like it had had a remap that even the authorised service garage couldn't spot, so in the end the whole ECU was replaced.
Happily, this did the trick, made the car slower admittedly, but it works properly now and I haven't had any similar problems since (two years and 26,000 miles later). Fingers crossed!
Thankfully all the above was done under the indie specialist's warranty.
Blimey, didn't realise I'd waffle on so much (I hardly ever post). Anyway, hope that's of some help.