Último Custo ou data de atualização do custo

SELECT
     TGFPRO."DESCRPROD" AS TGFPRO_DESCRPROD,
     TGFEST."CODEMP" AS TGFEST_CODEMP,
     TSIEMP."RAZAOABREV" AS TSIEMP_RAZAOABREV,
     TGFEST."CODPROD" AS TGFEST_CODPROD,
     TGFEST."CONTROLE" AS TGFEST_CONTROLE,
     TGFEST."DTVAL" AS TGFEST_DTVAL,
     TGFEST."ESTOQUE" AS TGFEST_ESTOQUE,
     TGFGRU."DESCRGRUPOPROD" AS TGFGRU_DESCRGRUPOPROD,
     TGFPRO."CODGRUPOPROD" AS TGFPRO_CODGRUPOPROD,
     TGFPRO."CODVOL" AS TGFPRO_CODVOL,
     TGFPRO."REFFORN" AS TGFPRO_REFFORN,
     TGFPRO."FABRICANTE" AS TGFPRO_FABRICANTE,
     (SELECT TGFCUS."CUSREP" FROM TGFCUS WHERE TGFCUS.CODPROD = TGFPRO.CODPROD AND
TGFCUS.DTATUAL = (SELECT MAX(CS.DTATUAL) FROM TGFCUS CS WHERE TGFPRO.CODPROD = CS.CODPROD)) AS CUSTO
FROM
     "PNEU"."TGFPRO" TGFPRO INNER JOIN "PNEU"."TGFEST" TGFEST ON TGFPRO."CODPROD" = TGFEST."CODPROD"
     INNER JOIN "PNEU"."TSIEMP" TSIEMP ON TGFEST."CODEMP" = TSIEMP."CODEMP"
     INNER JOIN "PNEU"."TGFGRU" TGFGRU ON TGFPRO."CODGRUPOPROD" = TGFGRU."CODGRUPOPROD"