MartinW,
Can you give us some additional details on your test setup. My first guess, without seeing a lot of detail is that you have the waitstates on the FlexBus set too high. The FlexBus can be a fast bus, if configured correctly, but also can be very slow if you are not careful.
If the only thing going on in the system is a DMA copy, then this number seems really large. Even if you have other things going on, this seems a bit large.
How are you configuring the DMA?
-JWW