Multi-Select String Parameter Values Are Converted To N'Value1', N'Value2' In Clause When Report Is Run

I understand that Multi-Select Parameters are converted behind the scenes to an In Clause when a report is executed. The problem that I have is that my multi-select string parameter is turned into an in claused filled with nvarchar/unicode expressions like:


Where columnName in (N'Value1', N'Value2', N'Value3'...)

This nvarchar / unicode expression takes what is already a fairly slow-performing construct and just drives it into the ground. When I capture my query with Profiler (so I can see the In Clause that is being built), I can run it in Management Studio and see the execution plan. Using N'Values' instead of just 'Value1', 'Value2','Value3' causes the query performance to drop from 40 seconds to two minutes and 40 seconds. It's horrible. How can I make it stop!!!?

Is there any way to force the query-rewriting process in Reporting Services to just use plain-old, varchar text values instead of forcing each value in the list to be converted on the fly to an Nvarchar value like this? The column from which I am pulling values for the parameter and the column that I am filtering are both just plain varchar.

Thanks,

TC