Do not run unnecessary instances of stored procedures.
Each time a stored procedure runs during a mapping, the session must wait for the stored procedure to complete in the database. You have two possible options to avoid this:
Reduce the row count.
Use an active transformation prior to the Stored Procedure transformation to reduce the number of rows that must be passed the stored procedure. Or, create an expression that tests the values before passing them to the stored procedure to make sure that the value does not really need to be passed.
Create an expression.
Most of the logic used in stored procedures can be easily replicated using expressions in the Designer.