I would say the whole of the air intake system could well be full of carbon and needs to be cleaned out. They are all in the same area, rhs front corner of the engine as you are looking at it from the front of the car, you will need to take a few bits off to do that.
Battery, air filter etc. Your fuel filter is behind the battery if it needs changing also.
Any mechanical parts needing decarbonising can be done by soaking rich washing up liquid and water, but nothing electrical. It just melts the carbon given a bit of time.