WHERE:(([Abramenko_Plazma_Test].[dbo].[_AccumRgT22].[_Fld21] as [T4].[_Fld21]<CONVERT_IMPLICIT(numeric(16,0),[@P3],0) 
OR [Abramenko_Plazma_Test].[dbo].[_AccumRgT22].[_Fld21] as [T4].[_Fld21]>CONVERT_IMPLICIT(numeric(16,0),[@P3],0)) 
AND 
([Abramenko_Plazma_Test].[dbo].[_AccumRgT22].[_Fld21] as [T4].[_Fld21]<CONVERT_IMPLICIT(numeric(16,0),[@P4],0) 
OR [Abramenko_Plazma_Test].[dbo].[_AccumRgT22].[_Fld21] as [T4].[_Fld21]>CONVERT_IMPLICIT(numeric(16,0),[@P4],0))

зачем здесь вторая конструкция после "AND", зачем оптимизатор ее добавляет? Да и в самом запросе: WHERE T4._Period = @P2 AND (T4._Fld21 <> @P3) AND (T4._Fld21 <> @P4)? 3 и 4 параметры оба равны 0.