The parameters passed into catalogue templates are not intended for raw Tempcode processing, so they need to be treated as text. i.e. they are not boolean values, they are text strings like 'Yes' or 'No'.
That's not entirely true because there are rawer parameters passed (I think like FIELD_7_RAW in this case) that may potentially work as boolean. But I can't remember OTTOMH exactly how it is.
The intention is you can find out for yourself using the {+START,PARAM_INFO}{+END} trick to get a temporary data dump.

This may work:
{+START,IF,{$EQ,{FIELD_7},Yes}}/{!CARD_ELITE}{+END}

Okay, that makes sense. Tried {FIELD_7_RAW} in my original code and that didn't seem to do the trick, but the example you gave last worked a treat. I only posted this here as I thought True was the same as Yes and it wasn't working.