We need to avoid the Superman III scenario. We should update fee from transaction and the currency conversion.
We currently only send information from audit files to CiviCRM if there is a refund or if a transaction is completely missing in the DB.
Some audit files have additional information, for example, underlying card type for a transaction only coded as 'Apple Pay' from the front end.
It's possible we could skip the log file grepping step for updates since that info should already exist. We will need to be careful that the update with a reduced field set doesn't overwrite any good data with defaults.
Note that this will increase queue load, so we would want to be able to turn this off at the audit parser during peak donation times.