Product's strapline is not included in the search (by default), but you can add it as searchable field, to do that, simply find/replace "LE_FieldID IN (1,2)" in your search stored procedure by "LE_FieldID IN (1,2,7)"
But if you want to change how the ranks given to results, its a tricky one!, you will need to study the search stored procedure in order to be able to play with the ranking formulas.