You need to get the codes read. By way of example - our V6 occasionally does this. Engine light on, no power, runs smoothly enough, no obvious faults. When you hook up the code reader, it complains about the throttle potentiometer (little plug in the driver's footwell). There is nothing wrong with the engine it is just saying "I have no idea what you are trying to do with the accelerator, so I am going to run a default (safe) map that is unlikely to damage anything".
So - get the codes read, and you will know more. Might be nothing to do with the engine. If you are going to keep the car (or Alfas generally) then a set of cables + multi ecu scan is a worthwhile investment that will cost about as much as going to a garage once to get the codes sorted.