>It returns a row, creating a unwanted resultset,
This does sound a lot like you are talking about the message line that gets returned after a t-sql staement executes, indicating the number of rows affected.
To eliminate this message from being returned by your stored procedures, put this statement at the start of your SP:
SET NOCOUNT ON
from BOL: "SET NOCOUNT ON eliminates the sending of DONE_IN_PROC messages to the client for each statement in a stored procedure. When using the utilities provided with Microsoft® SQL Server™ to execute queries, the results prevent "nn rows affected" from being displayed at the end Transact-SQL statements such as SELECT, INSERT, UPDATE, and DELETE."
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I don't think you can prevent what is known as the 'return value' (this is different from above) from being returned by your SP. On the other hand, I doubt very much that it is at the root of any performance problem.