showColumns for custom variables

I am trying to generate a report from visitor log using the API. I assume that column names are what is generated with an export. When entering in certain of the column names, the report either doesn’t generate results or does not include the specified columns. More importantly, I want to include custom variables and no matter how I enter those names, I cannot get them in the report (they are in the default).

For example, I included this string: visitorId,idVisit,type,url,pageTitle,pageIdAction,serverTimePretty,pageId,generationTime,icon,goalConversions,siteCurrency,siteCurrencySymbol,serverDate,visitServerHour

and only these showed in the report: idVisit visitorId goalConversions siteCurrency siteCurrencySymbol serverDate visitServerHour serverTimePretty

Please advise as to the correct syntax.

PSG