Speaking as a former officer I can reveal that many things are kept from the public so I am quite sure that Gonçalo has much in reserve.
So you are of the opinion that Amaral has held something back? His "Ace"?
Well, it is one of the features of the Portuguese penal code that everything pertinent to the investigation is placed in the public domain after the case has ended. Generally it will be at the local police station, but in the McCann case, due to the extent of interest, DVD was used. So anything he has held back would have to be something that his colleagues and the public prosecutor are unaware - otherwise it would have been acted on by his successor, or would have been included in the files.
If Amaral has been keeping actual evidence or facts "in reserve", and in particular anything which could lead to Madeleines discovery or evidence of wrongdoing by any party, then I am not convinced it would do him much good for obvious reasons. Witholding evidence, for a start.