Do you use 'sub-query'? from my try, DTA doesn't drill down into sub-query. I cheated the DTA while tuning by moving sub-query to main query, DTA gave different result.

set nocount on;

declare @bufferSPID table (EventType nvarchar(30), Parameter smallint, EventInfo nvarchar(4000));

declare @bufferBLOCKED table (EventType nvarchar(30), Parameter smallint, EventInfo nvarchar(4000));

declare @ret table (spid int, spidEventInfo nvarchar(4000), blocked int, blockedEventInfo nvarchar(4000), hostname...