I'm running on a dev box and I'm the only one on it, so I can do a check point and flush caches ect. to get reasonable timings.

I changed the report's dataset from SQL (text) to executing a stored procedure and I still get similar results. When I execute the stored proc in SSMS, it executes in 5-8 seconds, but the report takes 4 minutes to generate.

That sure makes it seem like it's something in SSRS and dynamic SQL as I first thought.

Rob