The optimization process and recommendations:

1. Avoid Correlated Subqueries (query line: 39): A correlated subquery is a subquery that contains a reference (column: idProduct) to a table that also appears in the outer query. Usually correlated queries can be rewritten with a join clause, which is the best practice. The database optimizer handles joins much better than correlated subqueries. Therefore, rephrasing the query with a join will allow the optimizer to use the most efficient execution plan for the query.
2. Avoid LIKE Searches With Leading Wildcard (query line: 45): The database will not use an index when using like searches with a leading wildcard (e.g. '%(9-12 Months)'). Although it's not always a satisfactory solution, please consider using prefix-match LIKE patterns (e.g. 'TERM%').

The optimized query:

SELECT
        P.idProduct,
        P.sku,
        P.description,
        P.price,
        P.listhidden,
        P.listprice,
        P.serviceSpec,
        P.bToBPrice,
        P.smallImageUrl,
        P.noprices,
        P.stock,
        P.noStock,
        P.pcprod_HideBTOPrice,
        P.pcProd_BackOrder,
        P.FormQuantity,
        P.pcProd_BTODefaultPrice,
        CAST(P.sDesc AS varchar (8000)) sDesc,
        0,
        0,
        P.pcprod_OrdInHome,
        P.sales,
        P.pcprod_EnteredOn,
        P.hotdeal,
        P.pcProd_SkipDetailsPage 
    FROM
        products P 
    INNER JOIN
        categories_products CP 
            ON P.idProduct = CP.idProduct 
    WHERE
        CP.idCategory = 494 
        AND active = -1 
        AND configOnly = 0 
        AND removed = 0 
        AND P.formQuantity = 0 
        AND (
            (
                SELECT
                    TOP 1 SP.stock 
                FROM
                    products SP 
                WHERE
                    SP.pcprod_ParentPrd = P.idProduct 
                    AND SP.description LIKE N'%(9-12 Months)' 
                    AND SP.removed = 0
            ) > 0
        ) 
    ORDER BY
        P.description ASC