What kind of reaction when you combine sodium bicarbonate and sodium acid pyrophosphate?
A quite readable explaination from a supplier of leavening agents : http://www.lallemand.com/BakerYeastNA/eng/PDFs/LBU%20PDF%20FILES/1_12CHEM.PDF

According to them, sodium acid pyrophosphate has indeed a "slow to very slow action, slightly bitter aftertast". But the bicarbonate will produce CO2 when reacting with the acid, regardless of heat.

I wouldn't use ammonia bicarbonate as its "ammonia taste limits [it] use to low-moisture products" : your batter might still contains too much moisture to get rid of the ammonia taste.