I've had a chip fitted since my 159 was more or less new, she's a 2.0ltr JTDM TI 2012, I bought one off eBay from The Italian Box Company, fitted it when she had done 3000 miles and have now done 36000 miles in 12 months.
The difference to the performance were noticeable, low end torque was way better, suddenly driving in 4th and 5th was so easy with huge surges of power when overtaking and more relaxed.
Fuel economy was improved as well, without the chip I would see 500 miles per tank, with the chip between 550/600 was the norm.
I never saw any black smoke and the car came alive in a very different kind of way.
I've just order a new more advanced chip from pro-bitz which arrives tomorrow, nothing wrong with the Italian Box chip but just fancied trying one that was allegedly more sophisticated.
If anyone interested I will have a new Italian Box chip for sale, I returned the old one under warranty saying the cable had come loose and they agreed to replace it for free, it will be programmed to the 2.0ltr JtDM engine so let me know if its of any interest.
I've never tried a remap but for me the chip option worked perfectly well, no issues with smoke etc and the Alfa was very settled with it on, would definitely recommend trying one.