sounds very similar to my issue :-(
Only other mod I have the car is a flexi-back exhaust system, so ill get that checked out too.. maybe pressure or something but doubt it...
So far dealer cannot fault the car, neither can Abarth/Fiat Techs...
Keep me posted about the plugs!
Oh- and as for my EML lights - mine were (tho, it now doesn't seem to be looking this all the time):
P0236 - Turbocharger Boost Sensor A Circuit Range/Performance
P0106 - Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem