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//catalog/templates/.default/element.php

<?$APPLICATION->IncludeComponent("api:similar.products", ".default", array(
      "IBLOCK_TYPE" => "sale",
      "IBLOCK_ID" => "1",
      "ITEMS_LIMIT" => "9",
      "SECTION_ID" => $arResult["VARIABLES"]["SECTION_ID"],
      "SECTION_CODE" => $arResult["VARIABLES"]["SECTION_CODE"],
      "ELEMENT_ID" => $arResult["VARIABLES"]["ELEMENT_ID"],
      "ELEMENT_CODE" => $arResult["VARIABLES"]["ELEMENT_CODE"],
   ),
   false
);?> 

//components/api/similar.products/component.php

....

 $arFilter = array(
   "IBLOCK_ID" => $arParams["IBLOCK_ID"],
   "ACTIVE" => "Y"
);
//Фильтр по группе из $arParams
if(!empty($arParams['SECTION_ID']))
   $arFilter['SECTION_ID'] = intval($arParams['SECTION_ID']);
elseif(!empty($arParams['SECTION_CODE']))
   $arFilter['SECTION_CODE'] = trim($arParams['SECTION_CODE']);


//Фильтр - все кроме текущего элемента
if(!empty($arParams['ELEMENT_ID']))
   $arFilter['!ID'] = intval($arParams['ELEMENT_ID']);
elseif(!empty($arParams['ELEMENT_CODE']))
   $arFilter['!CODE'] = trim($arParams['ELEMENT_CODE']);

....